In a controller for applying a first drive voltage signal to one of parallel-connected first and second switching elements to perform a predetermined switching operation of one of the first switching element and the second switching element according to change of a first drive voltage in one of the first and second switching elements, a voltage detector detects the first drive voltage of one of the first and second switching elements. A delaying unit delays an application of a second drive voltage signal to the other of the first switching element and the second switching element to perform the predetermined operation of the other of the first switching element and the second switching element according to change of a second drive voltage in the other thereof while the first drive voltage in one of the first and second switching elements is substantially a predetermined Miller voltage.