An endoscope system has an optical fiber configured to transmit illumination light emitted from a light source to the tip portion of a scope; a scanner configured to spirally scan a target area with the illumination light by vibrating the tip portion of the optical fiber; and an image generator configured to generate an observation image from image-pixel signals that are obtained from light reflected off of the target area. The endoscope system further has a resolution adjuster that adjusts a resolution of the observation image in accordance to a photographic state by controlling at least one of either a movement (drive) of the fiber tip portion or a sampling of the image-pixel signals.