The control device for controlling a power conversion circuit having voltage-controlled type switching elements includes a control unit generating conduction control signals for controlling conduction states of the switching elements in accordance with an external command, and a driver circuit applying a conduction control terminal of each of the switching elements with one of a first voltage having a value to turn on the switching elements and a second voltage having a value to turn off the switching elements in accordance with the conduction control signals. The driver circuit is configured to change at least one of the value of the first voltage and the value of the second voltage so that a voltage difference between the first and second voltages becomes large when the power loss of the switching elements is estimated to exceed a certain value.