In a putter shaft having a tip end and a butt end, a curvature of the putter shaft is represented by a curvature curve of the putter shaft which increases monotonously from the tip end to the butt end. The curvature curve is defined as a curve showing variation of the curvature in a longitudinal axis direction of the putter shaft in a state where a load acts on the tip end to deform the putter shaft with the putter shaft being fixed at the butt end.