An optical scanning apparatus including: an optical fiber that is configured to guide light from a light source to emit the light from a distal end thereof; a driver that is configured to oscillate the distal end of the optical fiber at a driving frequency in a direction intersecting a longitudinal axis of the optical fiber; a resonance-frequency detector that is configured to detect a resonance frequency of the distal end of the optical fiber; and a driving-frequency adjustor that is configured to adjust the driving frequency so that the ratio between the resonance frequency detected by the resonance-frequency detector and the driving frequency becomes constant.