A scanning endoscope system includes an optical fiber for guiding illumination light, an actuator configured to displace an irradiation position of the illumination light emitted through the optical fiber, and a controller. The controller generates a driving signal having periodicity for driving the actuator and supplies the driving signal via a predetermined signal line connected to the actuator, determines presence or absence of occurrence of a trouble in the predetermined signal line based either on a current value of an electric current flowing in the predetermined signal line at predetermined timing in a period for one cycle of the driving signal or a voltage value of a voltage applied to the actuator at the predetermined timing, and obtains a determination result that a trouble has occurred in the predetermined signal line when detecting that the current value continuously deviates predetermined times from a predetermined threshold range.
