Golf club head

1. A hollow golf club head having a volume equal to or greater than 400 cubic centimeters and comprising: a crown; a sole; and a continuously extending rib (X) having a mean value of a width, BR, equal to or less than 2 millimeters and a weight equal to or less than 5.0 grams,

wherein the rib (X) is provided on an inner surface of the head; the rib (X) is substantially parallel to a toe-heel direction; and when a maximum amplitude of vibration in a first-order mode in a state where the rib (X) is removed is defined as Ma 1 and an amplitude ratio with respect to the maximum amplitude Ma 1 is defined as Rh (%), disposal of the rib (X) satisfies the following items (a), (b), and (c):

(a) the rib (X) crosses at least one of high Rh regions having the amplitude ratio Rh of equal to or greater than 80%;

(b) no region having the amplitude ratio Rh of equal to or greater than 60% exists on a toe side than the rib (X); and

(c) no region having the amplitude ratio Rh of equal to or greater than 60% exists on a heel side than the rib (X); and

wherein the plurality of high Rh regions exist and the rib (X) crosses all of the high Rh regions.

2. The golf club head according to claim 1 , wherein a maximum amplitude point Pe 1 in the first-order mode in the state where the rib (X) is removed is located at a position other than the crown.

3. The golf club head according to claim 1 , wherein a maximum amplitude point Pm 1 in a first-order mode in a state where the rib (X) is disposed is located on the crown.

4. The golf club head according to claim 1 , wherein the rib (X) is provided on an inner surface of the sole.

5. The golf club head according to claim 1 , further comprising a side, wherein the rib (X) is provided on an inner surface of the sole and an inner surface of the side.

6. The golf club head according to claim 1 , wherein a height HR of the rib (X) is 2 mm or greater and 15 mm or less; and a mean value of a width BR of the rib (X) is 0.5 mm or greater.

7. The golf club head according to claim 1 , wherein a weight of the head is equal to or less than 200 g; a lateral moment of inertia of the head is equal to or greater than 5000 g·cm 2 ; a thickness of the sole is equal to or less than 1 mm; and a curvature radius of the sole is equal to or greater than 100 mm.

8. The golf club head according to claim 1 , wherein a maximum amplitude point Pm 1 in the first-order mode is located on the crown; and a maximum amplitude point of a second antinode is located on the sole.

9. The golf club head according to claim 1 , wherein when the rib (X) is removed, both a maximum amplitude point Pe 1 in the first-order mode and a maximum amplitude point Pe 2 in a second-order natural mode are located on the sole.

10. The golf club head according to claim 1 , wherein when the rib (X) is removed, a position of a first antinode in the first-order mode is the sole.

11. The golf club head according to claim 1 , wherein when the rib (X) is removed, a position of a first antinode in the first-order mode and a position of a second antinode in the first-order mode are the sole.

12. The golf club head according to claim 1 , wherein when the rib (X) is removed, a position of a first antinode in the first-order mode, a position of a second antinode in the first-order mode and a position of the first antinode in a second-order mode are the sole.

13. The golf club head according to claim 1 , wherein when the rib (X) is removed, a position of a first antinode in the first-order mode, a position of a second antinode in the first-order mode, a position of the first antinode in a second-order mode, and a position of the second antinode in the second-order mode are the sole.

14. The golf club head according to claim 1 , wherein a head width Wa is equal to or greater than 100 millimeters.

15. The golf club head according to claim 1 , wherein a head length Wc is equal to or greater than 100 millimeters.

16. The golf club head according to claim 1 , wherein a ratio Wr/Wc of a length Wr of the rib to the length Wc of the head is equal to or greater than 0.8.

17. The golf club head according to claim 1 , wherein a maximum amplitude point Pm 2 in the second order mode is located on the crown.

18. A hollow golf club head having a volume equal to or greater than 400 cubic centimeters and comprising: a crown; a sole; and a continuously extending rib (X) having a mean value of a width, BR, equal to or less than 2 millimeters and a weight equal to or less than 5.0 grams,

wherein the rib (X) is provided on an inner surface of the head; and, when a maximum amplitude of vibration in a first-order mode in a state where the rib (X) is removed is defined as Ma 1 and an amplitude ratio with respect to the maximum amplitude Ma 1 is defined as Rh (%), disposal of the rib (X) satisfies the following items (a), (b) and (c):

(a) the rib (X) crosses at least one of high Rh regions having the amplitude ratio Rh of equal to or greater than 80%;

(b) no region having the amplitude ratio Rh of equal to or greater than 60% exists on a toe side than the rib (X); and

(c) no region having the amplitude ratio Rh of equal to or greater than 60% exists on a heel side than the rib (X); and

wherein the plurality of high Rh regions exist and the rib (X) crosses all of the high Rh regions.