A bipolar cutter which can cut living tissues having various sizes more easily and can cauterize their cut surfaces in comparison with the conventional bipolar cutter is provided. The bipolar cutter includes a bipolar cutting treatment portion (18) having a pair of electrodes (48, 50) provided at a front-end portion of an insertion unit inserted in a body of a living thing, a guide portion (20) having a lead passage (20a) 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 (31) 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.
