An optical scanning method includes detecting a resonance frequency of a tip of a fiber while sweeping a vibration frequency of the tip of the fiber over a predetermined frequency range, the tip of the fiber being supported to allow oscillation, determining a driving frequency of the tip of the fiber on the basis of the detected resonance frequency, and scanning light over an object by causing the light to be emitted from the tip of the fiber while driving and vibrating the tip of the fiber at the driving frequency.