PURPOSE: To greatly improve the rounding accuracy of the cylindrical plain bearing by rounding a semi-finished product to a cylindrical shape by using a press device while turning a holder in common use as a core at every prescribed angle around the axial line by means of a step motor.

CONSTITUTION: The press device 7 is driven and a punch 7b is lowered to round the semi-finished product 1 between a recessed part of a semicylindrical shape and a recessed part of a die 7a. The rounding is executed by rising the punch 7b of the press device 7 and driving an air cylinder device 22 of a vertical driving device 18 to slightly rise the holder 4 in common use as the core, then properly rotationally driving the step motor 5 in the state of preventing the interference of the press device 7 and the semi-finished product 1 and precisely turning a revolving shaft via a belt 17d wound with a motor shaft to rotationally drive the holder 4 in common use as the core at the prescribed angle.