A damping device has a pin member inserted slidably in a cylindrical case member. The bottom of the case member has: a hole forming section in which an insertion hole is formed; and a slit for allowing the hole forming section to be expanded and deformed. The outer peripheral surface of the pin member and/or the inner peripheral surface of the hole forming section has a tapered section tilted relative to the axial direction. The movement of the pin member of being pressed into the insertion hole from the inside causes the outer peripheral surface of the pin member and the inner peripheral surface of the hole forming section to slide on each other along the tapered section, and as a result, the insertion hole is expanded.