A holder (50) for clamping a tool (100) includes a clamping mechanism (60) for clamping the tool (100), and an exposed portion (70). The clamping mechanism (60) is switchable between a clamping stateand an unclamping state. The clamping state is a state in which removal of the tool (100) from the holder (50) is hindered. The unclamping state is a state in which removal of the tool (100) from theholder (50) is allowed. The exposed portion (70) is exposed outside the holder (50) and directly or indirectly and mechanically linked to the clamping mechanism (60). The exposed portion (70) is pushed in one direction for movement to thereby switch the clamping mechanism (60) to the unclamping state.