Golf club head

1. A golf club head including a plurality of score lines on a face, comprising

a plurality of striations formed on said face and extending from a toe side to a heel side,

wherein a depth Dp of each striation satisfies:

10 μm≦D≦40 μm,

a cross-sectional shape of each striation is a isosceles trapezoid having an upper base at the face side and a lower base at a back side of the golf club head,

the upper base and lower base satisfy:

the upper base>the lower base, and

a width Pb of each protrusion formed between the striations and a width Wb of the lower base satisfies:

Pb<Wb.

2. The golf club head according to claim 1 , wherein a width Pu of an upper portion of each protrusion satisfy:

0<D≦15 μm.

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

a surface roughness of a region in said face with said striations satisfies in the arithmetic mean deviation of the profile Ra,

1.0 μm≦Ra≦5.0 μm.

4. The golf club head according to claim 1 , wherein an angle θ between side surfaces of striations adjacent to one another satisfies:

30 degrees≦θ≦140 degrees.

5. The golf club head according to claim 1 , wherein a pitch P between the protrusions satisfies:

100 μm≦P≦600 μm.

6. The golf club head according to claim 1 , wherein a cross section area A (inch 2 ) of said score line, a width W (inch) of said score line measured based on the 30 degrees measurement rule and a distance S (inch) between said score lines adjacent one another satisfy:

A /( W+S )≦0.003, and

edges of said score lines are formed to be positioned within a second virtual circle with a radius of 0.011 inches, the second virtual circle being concentric with a first virtual circle which internally touches said side surface and said face with a radius of 0.010 inches.