PURPOSE: To obtain an easily adjustable synchronizing signal generating circuit for an endoscope with a simple constitution, by detecting the displacement of a member which is associated operatively with camera release operation, and generating a syncrhonizing pulse through a delay means.

CONSTITUTION: When a diaphragm lever moves under the camera release operation, a photocoupler 28 turns off to trigger a monostable multivibrator 41. Consequently, a negative synchronizing pulse is outputted through a capacitor 44 after a delay time corresponding to the time constant determined by a resistance 42 and a capacitor 43 to ignite a discharge tube for a photographic light source. Consequently, the endoscope synchronizing signal generating circuit of a simple constitution which facilitates delay time adjustment by the resistance of a time constant circuit is obtained.