PROBLEM TO BE SOLVED: To obtain a high-quality bearing of good controllability with a simple machining in a short time, smooth in movement and with a low vibration, a low noise, and high rotation accuracy by inserting a mandrel having a desired groove shape on its peripheral face in the inside of the bearing, drawing the outside diameter of the bearing, and forming a convex or concave groove for generation of a dynamic pressure on the inside diameter surface of the bearing. SOLUTION: A mandrel equipped with a groove of desired shape on its outer periphery is inserted in the inside diameter of a metal bearing 10 of a circuit board 1 which also serves as the base for an outer rotor type brushless DC motor for a CD-ROM, and the metal bearing 10 is inserted in a housing 7, for drawing the outside diameter of the metal bearing 10, so as to form a convex herring bone groove for generation of a dynamic pressure on the inner face of the metal bearing 10. When it is assumed that the outside diameter of the bearing is D, the inside diameter of the bearing is d, the inside diameter of the drawing jig is A, and the diameter of the mandrel is B, it is preferable to satisfy (D-A)/D=0.005-0.035 and (d-B)/d A and d>B.