To provide a sheet cutting device capable of easily attaching a sensor, easily moving the sensor to a prescribed position according to the change of the sheet width, and excellently cutting a sheet by precisely detecting the existence of the end part of the sheet to be fed.

In the sheet cutting device, the end part 3b of a sheet running while wound around a roller 4 is detected by the sensor 2, and at the same time, a part 3a of the end of the sheet 3 is cut out of the whole width of the sheet 3 by a cutter 1 so that the width of the sheet is a prescribed value. The sensor 2 is a light reflecting type sensor in which a light projector part for irradiating light to the sheet end part 3b and a light receiving part for receiving the reflected light from the light projector part are integrated. The roller 4 is structured so that the light from the sensor 2 is mirror-reflected and the sheet 3 is structured so that the light from the sensor 2 is reflected irregularly. The sensor 2 is disposed at such a position where the irradiated light to the roller 4 can be mirror-reflected in the direction of receding from the sensor 2.