Method and apparatus for bidirectionally oscillating a spot of a laser beam incident upon a workpiece to be processed with the laser beam, wherein the laser beam generated by a laser source is reflected by a movable reflecting mirror which is bidirectionally pivoted about a first axis by an oscillating actuator, so that the reflected laser beam is incident upon the workpiece. The apparatus includes a rotary support member which supports the mirror and the oscillating actuator and which is rotatable about a second axis perpendicular to the first axis, and a rotating actuator for rotating the rotary support member about the second axis during bidirectional oscillation of the spot of the laser beam incident upon the workpiece, to thereby change an oscillating direction of the beam spot.