An ultrasonic endoscope includes a distal end rigid portion that is located at a distal end of an insertion section； a treatment tool lead-out portion that is disposed on a proximal end side of an ultrasonic transducer and that includes an erecting base housing portion that has an opening whose opening direction is toward one side in a first direction, an opening forming surface in which the opening is formed, and a treatment-tool erecting base that is disposed in an inside of the erecting base housing portion and that changes a lead-out direction of a treatment tool； and an observation window that is disposed in an observation means forming surface located on the proximal end side of the opening forming surface. The position of the observation window in the first direction is located on one side in the first direction relative to a one-side opening position of the opening.
