There is provided a matrix converter apparatus including both functions of outputting a step up voltage and outputting a step down voltage. In a matrix converter apparatus for directly connecting respective phases of a three phase alternating current power source (1) and respective phases of an output side by a bidirectional switch constituted by IGBT transistors or the like connected reversely in parallel therewith, controlling to output an alternating current power source voltage by a PWM control based on an output voltage instruction, and outputting an arbitrary direct current or alternating current voltage, respective reactors (61), (62), (63) inserted to be connected between the respective phases of the polyphase alternating current power source 1 and the bidirectional switches are included, and by controlling to ON/OFF the bidirectional switches, terminals of two or more of the reactors on a side of the bidirectional switch are shortcircuited, and thereafter opened to thereby step up an output voltage of the matrix converter apparatus. Further, when the terminals are switched from being shortcircuited to being opened, conduction paths of currents flowing in the respective reactors which have been shortcircuited are ensured by controlling to ON/OFF the bidirectional switch group (5) and a capacitor group (7).