Mode switching is reliably performed with a durable and small-sized configuration. A clutch pin (40) is provided in a reduction shaft (34) and configured to be slidable by an operation from outside, and a driven gear (38) is inserted onto the reduction shaft (34) and configured to be rotatable separately from the reduction shaft (34), so that a clutch mechanism is provided. By switching the clutch mechanism, a selection can be made between a hammer drill mode and a hammer mode. Meanwhile, the clutch pin (40) is configured to be slidable to a sliding position where the clutch pin (40) runs through the reduction shaft (34) so as to be capable of protruding upward beyond the reduction shaft (34), and at the sliding position, the clutch pin (40) engages with an engagement hole (46) provided on the tool holder (7) side so that a rotation of the tool holder (7) can be locked, whereby in the hammer mode, a selection can be further made between a neutral state where the clutch pin (40) does not engage with the engagement hole (46) and a rotation locked state where the clutch pin (40) engages with the engagement hole (46).