An endoscope apparatus includes: an insertion portion 2 a high-frequency knife a suction conduit 10 which sucks fluids from a suction port 6s a by-pass conduit 15 through which a gas D including a component derived from a living tissue passes a suction button 3a for opening and closing a flow passage of the suction conduit 10, which is provided at a location 10y of the suction conduit 10 a solenoid valve 17 that opens and closes a flow passage of the by-pass conduit 15 and a valve opening/closing portion 34a that causes the solenoid valve 17 to open and close based on an operation of the high-frequency knife.
