A medical device includes a snare wire advanceable and retractable inserted through a channel in an insertion portion that is inserted through an endoscope a substantially tubular cap member including a first portion and a second portion connected to a distal end of the insertion portion, the cap member having an annular distal end surface, the first portion being attachable to the distal end of the insertion portion in phase with the channel, and the cap member having an internal space formed by the first portion and the second portion and a guide member being linearly extended along an internal surface of the distal end side of the cap member at a side of the second portion, the guide member being configured to guide the snare wire to form a loop and to restrict a retraction of the snare wire toward the side of the insertion portion.
