A power tool is provided with a first unit, a second unit rotatable with respect to the first unit, a lock operation member and a lock cooperative switch. The lock operation member is configured to be operated by the user between a lock position and an unlock position, and configured to prevent rotation of the first and second units at the lock position and allow the rotation between the first and second units at the unlock position. The lock cooperative switch is disposed on the supply circuit of energy to the prime mover, and configured to enable the supply circuit when the lock operation member is at the lock position and cutoff the supply circuit when the lock operation member is at the unlock position.