A bipolar cutter includes a bipolar cutting treatment portion having a pair of electrodes provided at a front-end portion of an insertion unit inserted in a body of a living thing, a guide portion having a lead passage which captures a living tissue of a cutting target and which leads the living tissue to the treatment portion, the guide portion configured to vary a width of the passage, and a manipulation portion which manipulates the guide portion to vary the passage width. Alternatively, a shape of the lead passage is enlarged from its inner end to its outer end and a lead passage width regulating member being movable between the inner end and the outer end of the lead passage is included. Alternatively, a plurality of lead passages having widths being different from each other is included.
