To provide an endoscope system capable of appropriately observing a portion held to a treatment instrument of an endoscope.

An endoscope system includes: an endoscope device having a portion 60 to be inserted into a living body, and treatment instruments 62 and 63 disposed in the portion 60 for holding a subject (a living tissue) H; and an optical acoustic measuring device including light emitting means 67 and 68 for emitting light of such wavelength as to be absorbed inside the subject H to the subject H, and an acoustic wave detection means 11 for detecting an acoustic wave generated from the subject H with the emitted light, for measuring the subject H based on an acoustic wave detection signal output from the acoustic wave detection means 11. The light emitting means 67, 68, and the acoustic wave detection means 11 are mounted in such a state as to face the subject H side held to the treatment instruments 62 and 63.