The optical scanning apparatus includes a light amount reducing filter such as a neutral density filter which has transmittance ηnd satisfying an expression ηnd=(W1/W0)/(ηAOM×ηref×ηtra) and a light amount reducing function using absorption or reflection and which is disposed between a laser light source and an AOM on an optical path of laser light beam. In the expression, W0 denotes the amount of light emitted from the laser light source, W1 denotes the amount of light required for recording on a recording medium, ηAOM denotes diffraction efficiency in the AOM, ηref denotes a sum of reflectances of reflective optical elements located between the laser light source and a surface to be scanned, of the recording medium, and ηtra denotes a sum of transmittances of transmissive optical elements located between the laser light source and the surface to be scanned, other than transmittance of the neutral density filter.