A sheet cutter for cutting a sheet with a cutting blade held by a cutting blade elevating body which is elevated by one servo motor, including a pair of cutting blade elevating bodies; an elevation driving body for elevating the pair of cutting blade elevating bodies; a guide member for guiding the elevation of the pair of cutting blade elevating bodies; a holding body capable of holding the pair of cutting blade elevating bodies at an up position; and a transmission change-over device for selectively engaging the pair of cutting blade elevating bodies with the elevation driving body and selectively disengaging the pair of cutting blade elevating bodies from the elevation driving body, wherein one of the pair of cutting blade elevating bodies, which has been selected, is elevated by the servo motor.