To provide a high performance rotor and a method for drawing projections of the rotor.

Two discs having radii as the same as a radius of the rotor are prepared. A plate having an elliptical projection is wrapped by expandable cloth from the underside, is bonded to one of the discs and positioned to be fixed. Ink is applied to the cloth. While the face with cloth of the elliptical plate is brought into contact with the other plate so as to prevent both discs from sliding at a time of rotation, one disc is turned with its projection pressed from above to form a shape of a recess. This is the base of the shape of the recess. But this interfere with rotations, since the inside of the recess becomes a low pressure chamber at the time of rotation. Each corner of the recess has a shape in a manner that: space between the projection and the recess gradually expands from a point where the corner of the recess is on a line connecting the centers of axes; and space between the projection and the recess gradually expands from a point where the opposite corner of the recess is on the line connecting the centers of the axes at the time of inversion.