To determine leak of a vacuum chamber without connecting a leak detector after stopping the operation of a turbomolecular pump.

A motor control part 84 keeps a current to be supplied to a brushless motor 6 at a fixed value. A timer 89 measures the time in a period where the fixed current value is maintained by the motor control part 84. A rotation speed sensor 13 measures a motor rotation speed in the period where the fixed current value is maintained by the motor control part 84. A leak determination part 86 determines leak of a vacuum chamber 2 connected to an intake port side of the turbomolecular pump, on the basis of the time measured by the timer 89 and a difference between the maximum rotation speed and the minimum rotation speed measured by the rotation speed sensor 13.