A medical knife that can be assembled with different blade spacings, provided with only one handle includes a pair of side walls on respective sides of the handle, at least in the forward portions of the handle the side walls being formed individually on different handle-constituting parts and a pair of blades separately mounted on the insides of these side walls； and the handle before being assembled to constitute a medical knife is configured such that the two handle-constituting parts forward of a connecting part can be spread apart and closed together, centered on the connecting part, and such that the spacing distance between the two side walls is adjustable.
