PURPOSE: To efficiently machine a rocker arm excellent in dimensional accuracy and surface flatness.

CONSTITUTION: In the machining method of a rocker arm, a roller storing part 13 to store a roller 2 which is made in contact with a cam by separating approximately the center part of rocker arm 1, of which one end is a pivot part 11 as a rotating pivot and the other end is a valve pressing part 14, in lateral direction. Also the interval of the inner side surfaces 13a of the roller storing part 13 is manufactured slightly smaller than the finished dimensions at the stage material, and a cylindrical corrective roller with a diameter of finished dimension is pressed into the roller storing part 13. Then the corrective roller is forced out to correct the interval of the inner side surfaces 13a to the finished dimensions.