There is provided a crash box comprising a pedestal portion attached to one of two members that are placed in an inward-outward direction of a vehicle; and a bottomed tubular portion integrally molded with the pedestal portion and configured to include a base end portion that is arranged to rise from the pedestal portion and an extended portion that is extended from the base end portion and that has a leading end wall which forms a bottom of the tubular portion and which is attached to the other of the two members, wherein the tubular portion is configured such that a side wall of the extended portion has a smaller thickness than a thickness of a side wall of the base end portion.