PROBLEM TO BE SOLVED: To provide an ultrasonic endoscope capable of inhibiting chipping of a rubber member due to vibration to an opening of a pipeline in such a structure that the opening of the pipeline is opened and closed by the rubber member fitted in a fixed state to a fitting recessed part formed on the outer peripheral surface of a piston for a balloon suction pipeline.SOLUTION: An ultrasonic endoscope includes: a suction pipeline, one end of which is opened to the surface of an insertion part balloon suction pipelines 29, 39 independent of the suction pipeline a cylinder 35 a piston 40 for the balloon suction pipeline, the outer peripheral surface of which is provided with a fitting recessed part 45 a piston for a suction pipeline and a rubber member 48 which is opposite to the balloon side opening 39 of the balloon suction pipeline to thereby close up the opening and slides to a position different from that of the opening to open the opening. The rubber member includes: an opening and closing face 49 formed by a curved surface projected toward the inner peripheral surface of the cylinder to open and close the balloon side opening and a cutout part 50 which forms a clearance gap S in a space up to the inner peripheral surface of a fitting recessed part formed on at least one of both end parts in the sliding direction of the piston for the balloon suction pipeline on the opposite surface.
