An endoscope system includes: an image pickup device for picking up an object image; a drive control circuit for initializing and driving the image pickup device; and a monitoring portion for detecting abnormality of an image pickup signal from the image pickup device and outputting an initialization start signal to the drive control circuit. The monitoring portion compares a synchronization code, an optical black pixel value and an effective pixel value of the image pickup signal with respective thresholds indicating a normal range and a stipulated number of times or a stipulated number of pieces, and in a case of detecting abnormality of one of the synchronization code, the optical black pixel value and the effective pixel value, outputs the initialization start signal to the drive control circuit, and the drive control circuit initializes the image pickup device in a case of receiving the initialization start signal the monitoring portion.