Abstract: A slipper is formed with a sole defined by an outlined edge and having a predetermined length from the front end to the back end thereof, the sole being composed of a toe of a predetermined width defining the front end thereof, a foot inserting part having a predetermined minimum width located adjacent to the toe and progressively and symmetrically enlarged to a predetermined maximum width from the toe toward the back end of the sole, the foot inserting part having pressed bend lines extending slightly inside and along both edges thereof respectively to define the opposite marginal parts which may be spontaneously bent up when pressed to each other, a reduced part having both sides connected to the end of maximum width of the foot inserting part by edges extending with an acute angle from the end of maximum width of the foot inserting part to the reduced part on both sides thereof, a heel part progressively enlarged from the reduced part toward the back end of the sole.