Abstract: The present invention discloses a power transmission apparatus. The power transmission apparatus includes: an input shaft including a male screw portion formed thereon; a pair of input gears formed on the input shaft to be freely rotatable with the male screw portion being interposed therebetween; an output gear formed to be rotatable in a state of being linked with the pair of input gears; and a power interrupting unit screw-coupled to the male screw portion of the input shaft, and configured to rectilinearly reciprocate along the input shaft by a rotation of the input shaft to be selectively engaged with any one of the pair of input gears so as to transmit a power.