A head 4 includes a head body h1, a socket 10, and a weight body 12. The weight body 12 has an engaging part 32. The socket 10 has a first hole part 18 and a second hole part 20. The engaging part 32 can take an engaging position EP and a non-engaging position NP in the second hole part 20 by relative rotation of an angle θ. Hardness Hs of the second hole part 20 is D40 or greater and D58 or less. The second hole part 20 has a resistance surface 84 elastically deformed in the middle of the relative rotation. A longest sectional size of the engaging part 32 is defined as d1, and a distance between the resistance surfaces 84 opposed to each other is defined as F1, a ratio (F1/d1) is 0.935 or greater and 0.965 or less.