An endoscope system includes: a light transmitting section configured to transmit illuminating light generated by a light source and emit the light a driving section configured to allow the light transmitting section to be swung so as to draw trajectories corresponding to a predetermined scanning pattern a light receiving section configured to receive the illuminating light emitted within a predetermined period for the light transmitting section to be swung to a predetermined part of the predetermined scanning pattern a light detecting section configured to output a signal corresponding to an intensity of the illuminating light received by the light receiving section a determination section configured to detect fluctuations in a signal level of the signal outputted from the light detecting section and determine whether a pattern of the detected fluctuations of the signal level corresponds to a predetermined pattern of fluctuations and a control section configured to, if the pattern of fluctuations in the signal level within the predetermined time period does not correspond to the predetermined pattern of fluctuations, lower a quantity of the illuminating light supplied by the light source to a light guiding section.
