PURPOSE: To reduce uncomfortable feeling of passengers by promptly detecting abnormality generated in a control unit of an elevator driving induction motor to apply a brake to the induction motor.

CONSTITUTION: A speed detection value of an induction motor 4 output by a speed transmitter 12 and a speed command value set by a speed setter 11 are input to a subtracter 21 to calculate a difference between both the values. In a zero detector 22, an arithmetic result of the subtracter 21 is inputted, and when a value of this input is a value except zero, an abnormality signal is given to a timer 24 in the next step. The timer 24, when this abnormality signal is continued for a fixed time, judges a trouble generated in a control circuit of this elevator driving electric motor 4 to generate an alarm or to command a braking start relating to a brake 17. That is, abnormality of the control circuit is early detected to apply the brake 17 while an elevator speed is not so increased. In this way, an uncomfortable feeling of passengers can be reduced.