A power transmission, which transmits a driving force from a driving roller (112) to a driven roller (122) by using a friction roller (130). The power transmission includes a driving roller (112), a driven roller (122) spaced apart from the driving roller (112), and a friction roller (130) to transmit a driving force from the driving roller (112) to the driven roller (122). The friction roller (130) is disposed above a line connecting between centers of the driving roller (112) and the driven roller (122). With this construction, the friction roller (130) transmits the driving force in a state of being interposed between the driving rollers (122) and the driven rollers by rotation thereof, thereby allowing the power transmission to have a simplified structure, which does not require a separate pressing spring, and at the same time, to generate a minimum amount of power loss.