An optical scanning endoscope apparatus includes an optical fiber for illumination, a driver that drives the tip of the optical fiber for illumination in a Lissajous scan pattern, illumination lenses that irradiate an object of observation with irradiation light emitted from the tip of the fiber, a photodetector that detects light obtained from the object of observation by irradiation with the irradiation light and converts the light to an electrical signal, an image processor that generates an image based on the electrical signal output by the photodetector, and a phase adjustor that adjusts the phase of the drive waveform of the driver so as to correct a phase shift between the drive waveform of the tip of the fiber by the driver and the vibration waveform of the tip of the fiber.
