Misalignment detection method, misalignment detection device, and machine tool equipped with misalignment detection device

A misalignment detection device that detects a degree of misalignment of a center of gravity of a placed object on a rotary table relative to a first axis in a device that includes:

• the rotary table having a flat mounting surface, on which the placed object including a mount target is placed, and configured to rotate about the first axis orthogonal to the mounting surface and rotate about a second axis parallel to the mounting surface;
• and a drive motor configured to rotate the rotary table, the misalignment detection device comprising:
• a reference current storage unit configured to store, as a reference current value, a drive current supplied to the drive motor when the rotary table is rotated at a predetermined rotation speed about the first axis in a reference state in which the mounting surface is in a horizontal state and the mount target is not mounted;
• and
• a misalignment detection unit configured to acquire, as an actual current value, a drive current supplied to the drive motor when the rotary table with the mount target mounted thereon is rotated at the rotation speed about the first axis in an orientation-changed state in which the rotary table has been rotated about the second axis so that the mounting surface thereof forms a predetermined angle with respect to a horizontal surface, to calculate a difference value between the acquired actual current value and the reference current value stored in the reference current storage unit, and to detect the degree of misalignment based on the obtained difference value.