A lock body in a locked state is inserted radially inward of an outer surface. A stopper body in a contact state holds the lock body in an unlocked state. The stopper body in a non-contact state is retracted from the lock body. A pressing body is switchable between a standby state and a retracted state. The pressing body in the standby state selectively contacts a central shaft when an insertion portion is inserted in a support cylinder. The pressing body in the retracted state is retracted from the stopper body. An urging member urges the pressing body into the standby state, and urges the stopper body into the contact state. The urging member detachably engages the pressing body to the stopper body. Thus, the structure of the cutter holder is simple.