Golf club head

1. A golf club head having a hollow comprising

a face portion whose front face defines a clubface for hitting a ball,

the face portion comprising a central thicker portion provided in a center region thereof and a peripheral thinner portion provided around the central thicker portion and having a thickness smaller than that of the central thicker portion,

the peripheral thinner portion having an inner surface facing the hollow,

the inner surface of the peripheral thinner portion comprising a first region and a second region,

the first region being provided with a plurality of first grooves which extend straightly in a certain direction, and

the second region being provided with a plurality of second grooves which extend straightly in the different direction of first grooves.

2. The golf club head according to claim 1 , wherein

first grooves extend in parallel with each other.

3. The golf club head according to claim 1 or 2 , wherein

second grooves extend in parallel with each other.

4. The golf club head according to claim 1 or 2 , wherein

first grooves extend at right angles to second grooves.

5. The golf club head according to claim 1 or 2 , wherein

first grooves and second grooves each have a groove depth in a range of from 0.02 to 0.80 mm and a groove width in a range of from 0.1 to 3.0 mm.

6. The golf club head according to claim 1 or 2 , wherein

first grooves and second grooves each have an arc shape in a cross section intersecting with the longitudinal direction of each groove, and

the arc shape has a radius of curvature of from 1.0 to 5.0 mm.

7. The golf club head according to claim 1 or 2 , wherein

pitches between adjacent first grooves are in a range of from 1.0 to 1.5 times groove widths of first grooves, and

pitches between adjacent second grooves are in a range of from 1.0 to 1.5 times groove widths of second grooves.

8. The golf club head according to claim 1 or 2 , wherein

in a front view under a standard state that the club head is placed on a horizontal plane, so that a clubshaft center line inclines at its lie angle within a vertical plane, and the clubface inclines at its loft angle with respect to the vertical plane,

first grooves incline at angle of from 80 to 100 degrees with respect to the horizontal plane, and

second grooves incline at angle of from 0 to 10 degrees with respect to the horizontal plane.

9. The golf club head according to claim 8 , wherein

first grooves are provided with a toe side region and a heel side region of the inner surface of the peripheral thinner portion, and

second grooves are provided with a crown side region and a sole side region of the inner surface of the peripheral thinner portion.