A variable valve operating device using a valve-driving motor to vary open and close timings of at least one of an intake valve and an exhaust valve for an internal combustion engine, the variable valve operating device comprising: a first route constructed to supply an electric power from a low voltage accumulator to the valve-driving motor, where the low voltage accumulator is capable of storing a low voltage obtained by stepping down a high voltage supplied from a high voltage power source by means of an electric power conversion circuit; a second route constructed to supply an electric power as the low voltage obtained by stepping down the high voltage by means of the electric power conversion circuit without passing through the low voltage accumulator; and a controller configured to control the valve-driving motor, which receives the supply of electric power via either of the first route or the second route, to vary the open and close timings of the at least one of the intake valve and the exhaust valve on a start of the internal combustion engine, in response to a requirement for varying the open and close timings set at a stop time of the internal combustion engine, the variable valve operating device further having: a temperature detector configured to measure a temperature (Tw) of the internal combustion engine; characterized by a route switchover mechanism configured to activate or deactivate the second route for supplying the electric power to the valve-driving motor; wherein, when the temperature (Tw) of the internal combustion engine measured by the temperature detector is within a predetermined low temperature range, the controller is configured to control the route switchover mechanism to activate the second route for supplying the electric power to the valve-driving motor, while controlling the valve-driving motor, which is configured to receive the supply of electric power via either of the first route or the second route, to vary the open and close timings; the route switchover mechanism being configured to switch on/off a switch provided on the second route to select the electric power supply to the valve driving motor between the first route and the second route. a first route constructed to supply an electric power from a low voltage accumulator to the valve-driving motor, where the low voltage accumulator is capable of storing a low voltage obtained by stepping down a high voltage supplied from a high voltage power source by means of an electric power conversion circuit; a second route constructed to supply an electric power as the low voltage obtained by stepping down the high voltage by means of the electric power conversion circuit without passing through the low voltage accumulator; and a controller configured to control the valve-driving motor, which receives the supply of electric power via either of the first route or the second route, to vary the open and close timings of the at least one of the intake valve and the exhaust valve on a start of the internal combustion engine, in response to a requirement for varying the open and close timings set at a stop time of the internal combustion engine, the variable valve operating device further having: a temperature detector configured to measure a temperature (Tw) of the internal combustion engine; characterized by a route switchover mechanism configured to activate or deactivate the second route for supplying the electric power to the valve-driving motor; wherein, when the temperature (Tw) of the internal combustion engine measured by the temperature detector is within a predetermined low temperature range, the controller is configured to control the route switchover mechanism to activate the second route for supplying the electric power to the valve-driving motor, while controlling the valve-driving motor, which is configured to receive the supply of electric power via either of the first route or the second route, to vary the open and close timings; the route switchover mechanism being configured to switch on/off a switch provided on the second route to select the electric power supply to the valve driving motor between the first route and the second route. a temperature detector configured to measure a temperature (Tw) of the internal combustion engine; characterized by a route switchover mechanism configured to activate or deactivate the second route for supplying the electric power to the valve-driving motor; wherein, when the temperature (Tw) of the internal combustion engine measured by the temperature detector is within a predetermined low temperature range, the controller is configured to control the route switchover mechanism to activate the second route for supplying the electric power to the valve-driving motor, while controlling the valve-driving motor, which is configured to receive the supply of electric power via either of the first route or the second route, to vary the open and close timings; the route switchover mechanism being configured to switch on/off a switch provided on the second route to select the electric power supply to the valve driving motor between the first route and the second route.