PURPOSE: To perform easy and safe alignment of a machining tool with the machining position of a work without stopping operation of the machining tool.

CONSTITUTION: A support part 4 is vertically movably arranged independently away from a main spindle 2 on which a machining tool 3 is attached. A plurality of visible radiation laser devices 1 are mounted on the support part 4 so that distances from the main spindle 2 centering around the main spindle 2 are equal to each other, radiation directions are inwardly inclined in a given angle arc, and a coincidence point between radiation positions indicates the machining position of a work. An alignment work is completed only in a way that the coincidence point between the radiation positions of the visible radiation laser device 1 is caused to coincide with the machining position of the work through regulation of the height of the support part 4.