A medical treatment instrument includes a tube-shaped elongated main body and an insertion guide part mounted to a distal end of the elongated main body. The insertion guide part includes a frame body mounted to a distal portion of the elongated main body and a flexible bridge portion which is disposed so as to bridge points of an end edge of the frame body, the flexible bridge portion including a linear body or band-shaped body projecting in a distal direction beyond the elongated main body.
