Endoscope having observation window through which treatment tool and distal end of outer casing are viewable

An endoscope comprising:

• a distal end portion that is provided on a distal end side of an insertion section and that has a distal end, a proximal end, and a longitudinal axis;
• an ultrasonic transducer that is provided in the distal end portion and includes a plurality of ultrasonic vibrators;
• a treatment tool lead-out port that is formed in the distal end portion and that leads out a treatment tool inserted through an inside of the insertion section;
• an elevator support member that is provided in the distal end portion, and rotatably supports an elevator configured to control a lead-out direction in which the treatment tool is led out from the treatment tool lead-out port;
• and
• an observation window that is provided in the distal end portion,
• wherein at least a part of the ultrasonic transducer and the treatment tool are within an observation range of the observation window, and the observation range includes the treatment tool regardless of whether the elevator is either at a lowered position or is at an elevated position.