A head 2 is hollow. The head 2 includes a face part 4, a crown part 6 and a sole part 8. Ribs 20 and 22 are provided on the inner surface of the head. The ribs 20 and 22 have a height being greater than a thickness. The ribs 20 and 22 are separated from the face part, and are separated from the crown part. An extending direction of the rib 20 is inclined with respect to a front-back direction of the head. The rib 20 has a height change part 30 formed in a face side end part of the rib 20, the height change part 30 having a height gradually lowered as approaching a rib end part. The rib 20 extends toward a heel side in the direction of a backside of the head.