An optical scanning apparatus includes a light source and a structure for performing light-power control for the light source, the structure including a light-power-detection optical unit that establishes an optically conjugate relationship between a deflecting surface of a deflecting unit and a light-receiving surface of a light-power detector in a main-scanning plane. Accordingly, the storage time of a light beam on the light-power-detection optical unit is increased and variation in the power of light emitted by the light source due to heat generated by the light source and environmental variation is accurately detected.