To provide a power transmission structure of a motor that surely transmits the revolution of the motor to a rear stage via a resin gear at low cost.

This structure comprises the resin gear 3 made of a resin material that has a circular recessed portion on the tip-end surface that crosses an output shaft of the motor perpendicularly to transmit the revolution of the motor to one or more stages of gears, and a fixing plate 4, made of a material whose thermal expansion coefficient is smaller than that of the resin material, having line surfaces 4a-4e in external shapes and a shaft hole 4a which is press-fitted into the output shaft of the motor. The fixing plate is integrated with the resin gear by being inputted into the bottom surface side of the circular recessed portion formed on the tip of the resin gear, by being fixed by press-fitting on to output shaft of the motor with the resin gear, and by welding the tip of the circular recessed portion in this state.