An endoscope system includes an endoscope and a suction unit. The endoscope includes an insertion portion configured to be inserted into a subject, an operation portion provided on a proximal end side of the insertion portion, and an angle knob provided on the operation portion for operating the bending portion; and an opening provided in the operation portion, wherein the opening is connected to a lumen provided in the endoscope. The suction unit includes a suction conduit, a protrusion inserted into the opening, and a suction button. In a side view perpendicular to an axis of rotation of the angle knob, a center of a top surface of the suction button, a center of the opening, and the angle knob are arranged along an imaginary straight line with the center of the opening located between the center of the top surface of the suction button and the angle knob.