PURPOSE: To divide the phases of the first and fourth crank pins of a crank shaft or second and third crank pins, where there is no phase division spot, such as holed and notches, on the rotation central line of a main spindle by a phase dividing device, the number of constituting elements of which is low, with higher precision.

CONSTITUTION: The side shoe 91 of a stabilizing device is mounted. Rotation of the center of the journal Wj of a crank pin Wa to be divided is constrained by a phase dividing side arm 92 moved to a phase dividing position by a positioning means, and guided to the vicinity of the rotation center of a main spindle. The phase dividing side part arm 92 is moved to a phase determining position by a positioning means to effect determination of a phase.