To provide a control system for an elevator that effectively uses electric energy accumulated in a power accumulator in the event of a service interruption by changing an operation mode while monitoring the residual of the power accumulator.

The control system for an elevator comprises a converter for rectifying alternating-current power from an alternating-current power source to convert it into direct-current power, an inverter for converting the direct-current power from the converter into alternating-current power of a variable voltage and frequency and driving an electric motor to operate an elevator, the power accumulator interposed in a direct-current bus between the converter and the inverter to accumulate the direct-current power from the direct-current bus during a regenerative operation of the elevator and to supply the accumulated direct-current power to the direct-current bus during a power running operation, a charging/discharging controlling circuit for controlling the charging/discharging of the power accumulator relative to the direct- current bus, a charging/discharging state measuring circuit for measuring the charging/ discharging state of the power accumulator, and a controlling means for changing an operation mode during an operation under a service interruption from the alternating-current power source according to the output of the measuring circuit.