It is an object of the invention to provide a reciprocating power tool having a further improved power transmitting mechanism for converting a rotating output of a driving motor into linear motion in the axial direction of the tool bit. The representative reciprocating power tool may comprise a tool bit, a driving motor and a power transmitting mechanism that converts a rotating output of the driving motor into linear motion in the axial direction of the tool bit. The power transmitting mechanism includes an internal gear, a planerary gear, a power transmitting part, a rotation preventing mechanism and an internal gear rotation lock. Further, an internal gear rotation lock prevents the internal gear from rotating in a direction opposite to said predetermined direction. Therefore, the internal gear rotated only in one direction via the internal gear rotation lock and as a result, the internal gear can be reliably locked in a predetermined position without causing rattling. Thus, the accuracy of the locked position of the internal gear can be enhanced and stable operation can be realized.