Provided is an ultrasonic endoscope that can observe even a proximal end portion side of a treatment tool in the field of view of an observation window. The ultrasonic endoscope includes a distal end rigid portion 34 that is located at a distal end of an insertion section 12； a treatment tool lead-out portion that is disposed on a proximal end side of an ultrasonic transducer 50 and that includes an erecting base housing portion 62 that has an opening 58 whose opening direction is toward one side in a first direction, an opening forming surface 70 in which the opening 58 is formed, and a treatment-tool erecting base 60 that is disposed in an inside of the erecting base housing portion 62 and that changes a lead-out direction of a treatment tool； and an observation window 44 that is disposed in an observation means forming surface 72 located on the proximal end side of the opening forming surface 70. The position of the observation window 44 in the first direction is located on one side in the first direction relative to a one-side opening position of the opening 58.
