An ultrasound endoscope comprising: an insertion portion configured to be inserted into a subject; an ultrasound transmitting and receiving portion (11, 11A) that is arranged at a distal end portion of the insertion portion, and includes an ultrasound transmitting and receiving surface for transmitting and receiving ultrasound, the ultrasound transmitting and receiving portion being an ultrasound probe portion of an electronic radial type; a cylindrical balloon (21, 31, 31A, 31B) closed at a distal end that is arranged to cover the ultrasound transmitting and receiving portion, the balloon made of an elastic member and comprising a balloon main body portion configuring a cylindrical storing portion that is configured to store an ultrasound medium, a first annular portion having a Young's modulus larger than the Young's modulus of the balloon main body portion and framing a proximal end side of the balloon main body portion, a second annular portion having a Young's modulus larger than a Young's modulus of the balloon main body portion and framing a distal end side of the balloon main body portion, and a distal end cover portion configuring a film portion that closes the distal end side of the balloon main body portion; a first balloon groove that is arranged at a distal end of the ultrasound transmitting and receiving portion and in which the second annular portion is fit to lock the balloon, the first balloon groove being formed over an entire circumference of the ultrasound transmitting and receiving portion; a second balloon groove that is arranged at a proximal end side of the ultrasound transmitting and receiving portion and in which the first annular portion is fit to lock the balloon, the second balloon groove being formed over the entire circumference of the ultrasound transmitting and receiving portion; a water feeding/draining groove arranged on a distal end side of the second balloon groove for a balloon communicating with an outside; a distal end face that has a circular shape and is provided on a distal end side of the ultrasound transmitting and receiving portion to be spaced apart from the ultrasound transmitting and receiving surface, the distal end face being covered with the distal end cover portion; and at least one convex portion that has a maximum outer diameter of 20 to 80% of a diameter of the distal end face in a plan view of the distal end face, and is in contact with an inner side surface of the distal end cover portion to increase a frictional force between a surface of the distal end cover portion and a finger when the cylindrical balloon is attached to the distal end portion of the insertion portion, the at least one convex portion being provided on the distal end face and having a spherical crown shape. an insertion portion configured to be inserted into a subject; an ultrasound transmitting and receiving portion (11, 11A) that is arranged at a distal end portion of the insertion portion, and includes an ultrasound transmitting and receiving surface for transmitting and receiving ultrasound, the ultrasound transmitting and receiving portion being an ultrasound probe portion of an electronic radial type; a cylindrical balloon (21, 31, 31A, 31B) closed at a distal end that is arranged to cover the ultrasound transmitting and receiving portion, the balloon made of an elastic member and comprising a balloon main body portion configuring a cylindrical storing portion that is configured to store an ultrasound medium, a first annular portion having a Young's modulus larger than the Young's modulus of the balloon main body portion and framing a proximal end side of the balloon main body portion, a second annular portion having a Young's modulus larger than a Young's modulus of the balloon main body portion and framing a distal end side of the balloon main body portion, and a distal end cover portion configuring a film portion that closes the distal end side of the balloon main body portion; a first balloon groove that is arranged at a distal end of the ultrasound transmitting and receiving portion and in which the second annular portion is fit to lock the balloon, the first balloon groove being formed over an entire circumference of the ultrasound transmitting and receiving portion; a second balloon groove that is arranged at a proximal end side of the ultrasound transmitting and receiving portion and in which the first annular portion is fit to lock the balloon, the second balloon groove being formed over the entire circumference of the ultrasound transmitting and receiving portion; a water feeding/draining groove arranged on a distal end side of the second balloon groove for a balloon communicating with an outside; a distal end face that has a circular shape and is provided on a distal end side of the ultrasound transmitting and receiving portion to be spaced apart from the ultrasound transmitting and receiving surface, the distal end face being covered with the distal end cover portion; and at least one convex portion that has a maximum outer diameter of 20 to 80% of a diameter of the distal end face in a plan view of the distal end face, and is in contact with an inner side surface of the distal end cover portion to increase a frictional force between a surface of the distal end cover portion and a finger when the cylindrical balloon is attached to the distal end portion of the insertion portion, the at least one convex portion being provided on the distal end face and having a spherical crown shape.