A failure detecting apparatus for detecting a failure in a driving circuit for an electric lifting-lowering device, the driving circuit having a three-phase alternating-current power supply circuit and supplying driving electric power from the three-phase alternating-current power supply circuit to a three-phase alternating-current electric motor and a brake through a motor contactor and a brake contactor, respectively, the failure detecting apparatus comprising: a detecting circuit ( 6a, 6b, 6c, 6d, 6e) connected in parallel to each on/off mechanical contact ( 2a, 2b, 2c, 4a, 4b) or on/off semiconductor device of the motor contactor and/or the brake contactor and outputting a pulse signal synchronized with an alternating current from the three-phase alternating-current power supply circuit; and a signal processing means having a normal-abnormal detecting function, the signal processing means processing the pulse signal from the detecting circuit ( 6a, 6b, 6c, 6d, 6e) and detecting a normal or abnormal condition of each on/off mechanical contact ( 2a, 2b, 2c, 4a, 4b) or on/off semiconductor device of the motor contactor and/or the brake contactor; the motor contactor being a three-phase contactor; the signal processing means being capable of processing the pulse signal from the detecting circuit ( 6a, 6b, 6c) connected in parallel to each on/off mechanical contact ( 2a, 2b, 2c) or on/off semiconductor device of the motor contactor, which is the three-phase contactor, and detecting a reverse phase of three-phase alternating-current electric power to be supplied to the three-phase alternating current electric motor by the normal-abnormal detecting function; and the detecting circuit ( 6a, 6b,6c) having a unilateral photocoupler comprising a light-emitting diode and a phototransistor, in which the light-emitting diode is caused to emit light by an alternating-current voltage applied to the on/off mechanical contact ( 2a, 2b, 2c, 4a, 4b) or the on/off semiconductor device, and the light is converted into an electric pulse signal by the phototransistor. a detecting circuit ( 6a, 6b, 6c, 6d, 6e) connected in parallel to each on/off mechanical contact ( 2a, 2b, 2c, 4a, 4b) or on/off semiconductor device of the motor contactor and/or the brake contactor and outputting a pulse signal synchronized with an alternating current from the three-phase alternating-current power supply circuit; and a signal processing means having a normal-abnormal detecting function, the signal processing means processing the pulse signal from the detecting circuit ( 6a, 6b, 6c, 6d, 6e) and detecting a normal or abnormal condition of each on/off mechanical contact ( 2a, 2b, 2c, 4a, 4b) or on/off semiconductor device of the motor contactor and/or the brake contactor; the motor contactor being a three-phase contactor; the signal processing means being capable of processing the pulse signal from the detecting circuit ( 6a, 6b, 6c) connected in parallel to each on/off mechanical contact ( 2a, 2b, 2c) or on/off semiconductor device of the motor contactor, which is the three-phase contactor, and detecting a reverse phase of three-phase alternating-current electric power to be supplied to the three-phase alternating current electric motor by the normal-abnormal detecting function; and the detecting circuit ( 6a, 6b,6c) having a unilateral photocoupler comprising a light-emitting diode and a phototransistor, in which the light-emitting diode is caused to emit light by an alternating-current voltage applied to the on/off mechanical contact ( 2a, 2b, 2c, 4a, 4b) or the on/off semiconductor device, and the light is converted into an electric pulse signal by the phototransistor.