PURPOSE: To reduce noise by providing an apparatus with means for expanding the width of a required output frequency corresponding to each bank of a switching logical pattern storage element with the increase of said output frequency.

CONSTITUTION: An inverter control circuit is composed of a rate multiplier 2, a counter 3, ROM 4 being a storage element, and a waveform-composing circuit 5 to ON-OFF control the switching element of main circuit according to a logical pattern. Then, said control circuit is provided with CPU1, which inputs an inverter output frequency command S1, performs various operations, and inputs the outputs of said operations to said rate multiplier 2 and to the ROM. Thus, the frequency bandwidth corresponding to each bank for an output frequency is successively expanded according to the indrease of said output frequency, and the unequal division of a frequency band is performed in the manner of controlling the range of variation width of a carrier frequency and said output voltage within a required value. As a result, it is possible to reduce the range of variation of said carrier frequency and that of said output frequency.