| CPC A61B 8/12 (2013.01) [A61B 1/06 (2013.01); A61B 1/2676 (2013.01); A61B 8/445 (2013.01)] | 17 Claims |

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1. An ultrasonic endoscope comprising:
a distal end part body provided on a distal end side of an insertion part; and
an ultrasound transducer provided on a distal end side of the distal end part body,
wherein an outer peripheral surface of the distal end part body includes
a first surface that is provided on a proximal end side of the ultrasound transducer and that extends along a longitudinal axis of the insertion part,
a second surface that is provided on a proximal end side of the first surface and that extends along the longitudinal axis, the second surface being positioned on a one direction side of a first direction perpendicular to the longitudinal axis with respect to the first surface, and
a stepped surface that connects the proximal end side of the first surface and a distal end side of the second surface, and
in a case where a direction perpendicular to both the longitudinal axis and the first direction is referred to as a second direction, an angle indicating an irradiation range of an ultrasonic wave emitted from the ultrasound transducer in a case where the distal end part body is viewed from a second direction side is referred to as an effective angle, and an intersection of a tangent line in contact with the ultrasound transducer and in contact with the stepped surface at a position closest to the one direction side and the ultrasound transducer is referred to as a first intersection, the first intersection is included in a range of 1/3 on a proximal end side of the effective angle.
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