Golf club

1. A golf club comprising:

a head having a hosel part;

a shaft; and

a reverse-tapered engagement part disposed at a tip portion of the shaft,

wherein:

the reverse-tapered engagement part includes a sleeve having a reverse-tapered shape and being fixed to the tip portion of the shaft, and a reverse-tapered outer surface;

the hosel part includes a hosel hole, and a hosel slit which is provided on a side of the hosel hole and enables the shaft to pass through the hosel slit;

the hosel hole has a reverse-tapered inner surface having a shape corresponding to a shape of the reverse-tapered outer surface;

either one of the reverse-tapered outer surface and the reverse-tapered inner surface has an abutting engagement surface;

the other of the reverse-tapered outer surface and the reverse-tapered inner surface has a first abutting surface and a second abutting surface;

a first state in which the abutting engagement surface abuts on the first abutting surface is formed when the reverse-tapered outer surface is set on a first rotation position, and a second state in which the abutting engagement surface abuts on the second abutting surface is formed when the reverse-tapered outer surface is set on a second rotation position; and

an axial direction position of the reverse-tapered outer surface with respect to the reverse-tapered inner surface in the first state is different from that of the second state, and a club length is adjusted by the difference.

2. The golf club according to claim 1 , wherein

the reverse-tapered outer surface further has a non-abutting engagement surface in addition to the abutting engagement surface,

the reverse-tapered outer surface is a pyramid outer surface, and the abutting engagement surface and the non-abutting engagement surface are alternately arranged on the pyramid outer surface;

a radial direction position of the abutting engagement surface is located outside with respect to a radial direction position of the non-abutting engagement surface; and

the reverse-tapered inner surface is a pyramid inner surface corresponding to the pyramid outer surface, and the first abutting surface and the second abutting surface are alternately arranged on the pyramid inner surface.

3. The golf club according to claim 2 , wherein

the pyramid outer surface is an eight-sided pyramid surface, and

the pyramid inner surface is an eight-sided pyramid surface.

4. The golf club according to claim 1 , wherein the reverse-tapered engagement part is constituted with the sleeve, and at least one spacer externally fitted to the sleeve.

5. The golf club according to claim 4 , wherein an axis line of an inner surface of the spacer is inclined or parallel eccentric with respect to an axis line of an outer surface of the spacer.

6. The golf club according to claim 1 , wherein an axis line of an inner surface of the sleeve is inclined or parallel eccentric with respect to an axis line of an outer surface of the sleeve.

7. The golf club according to claim 1 , wherein the head further includes a falling-off prevention part which regulates movement of the reverse-tapered engagement part in an engagement releasing direction.

8. The golf club according to claim 1 , wherein an outer surface of the sleeve is the reverse-tapered outer surface.

9. The golf club according to claim 1 , wherein the reverse-tapered outer surface has a sectional shape of a substantially polygon.

10. The golf club according to claim 1 , wherein the reverse-tapered outer surface has a sectional shape of a substantially regular polygon.

11. The golf club according to claim 1 , wherein an area of a figure including a sectional line of the reverse-tapered outer surface as an outer edge is larger as going to a sole side.