Abstract: There are provided an electric storage device (11), inverter devices (7, 10), a converter device (12) for converting the voltage of circuits to which the inverter devices (7, 10) are connected, a motor generator (6) for driving a hydraulic pump (4) using alternate current from the inverter device (7), a motor (9) for driving wheels (61) using alternate current from the inverter device (10), and a control device (200) for controlling the inverter devices (7, 10). When any of the devices necessary for supplying the current to the motor (9) has developed a failure, the control device (200) drives the motor (9) by getting another normal device to perform another process corresponding to the process that has been performed by the malfunctioned device before the failure. This makes it possible to continue travel movement even when part of a travel power supply system has developed a failure.