A power converting apparatus comprising: a first inverter circuit (1, 21, 31); and a second inverter circuit (2, 22, 32) wherein AC side output terminals of the first inverter circuit (1, 21, 31) and AC side output terminals of the second inverter circuit (2, 22, 32) are connected in series, and AC power having a prescribed voltage waveform obtained by combining outputs of the first and second inverter circuits (1, 21, 31, 2, 22, 32) is supplied to a load (9, 29, 39); the apparatus being characterized in that; the first inverter circuit (1, 21, 31) is provided with a first DC voltage source (5, 25, 35) and a plurality of Si semiconductor switching devices (3, 4, 23, 24, 33, 34), and the second inverter circuit (2, 22, 32) is provided with a second DC voltage source (8, 10, 28, 38) and a plurality of non-Si semiconductor switching devices (6, 7, 26, 27, 36, 37), wherein the voltage (Vdc-main) of the first DC voltage source (5, 25, 35) is higher than the voltage (Vdc-sub) of the second DC voltage source (8, 10, 28, 38), wherein the switching frequency at which the first inverter circuit (1, 21, 31) is driven is lower than the switching frequency at which the second inverter circuit (2, 22, 32) is driven, wherein SiC MOSFETs are used as the individual non-Si semiconductor switching devices (6, 26, 36) in the second inverter circuit (2, 22, 32); and wherein the ratio of the sum of two kinds of on-voltages of the Si semiconductor switching devices (3, 23, 33) in the first inverter circuit (1, 21, 31) and the non-Si semiconductor switching devices (6, 26, 36) in the second inverter circuit (2, 22, 32) to the sum of DC voltages of the first DC voltage source (5, 25, 35) and the second DC voltage source (8, 10, 28, 38) is smaller than the ratio of the on-voltage of the non-Si semiconductor switching devices (6, 26, 36) to the DC voltage of the second DC voltage source (8, 10, 28, 38). a first inverter circuit (1, 21, 31); and a second inverter circuit (2, 22, 32) wherein AC side output terminals of the first inverter circuit (1, 21, 31) and AC side output terminals of the second inverter circuit (2, 22, 32) are connected in series, and AC power having a prescribed voltage waveform obtained by combining outputs of the first and second inverter circuits (1, 21, 31, 2, 22, 32) is supplied to a load (9, 29, 39); the apparatus being characterized in that; the first inverter circuit (1, 21, 31) is provided with a first DC voltage source (5, 25, 35) and a plurality of Si semiconductor switching devices (3, 4, 23, 24, 33, 34), and the second inverter circuit (2, 22, 32) is provided with a second DC voltage source (8, 10, 28, 38) and a plurality of non-Si semiconductor switching devices (6, 7, 26, 27, 36, 37), wherein the voltage (Vdc-main) of the first DC voltage source (5, 25, 35) is higher than the voltage (Vdc-sub) of the second DC voltage source (8, 10, 28, 38), wherein the switching frequency at which the first inverter circuit (1, 21, 31) is driven is lower than the switching frequency at which the second inverter circuit (2, 22, 32) is driven, wherein SiC MOSFETs are used as the individual non-Si semiconductor switching devices (6, 26, 36) in the second inverter circuit (2, 22, 32); and wherein the ratio of the sum of two kinds of on-voltages of the Si semiconductor switching devices (3, 23, 33) in the first inverter circuit (1, 21, 31) and the non-Si semiconductor switching devices (6, 26, 36) in the second inverter circuit (2, 22, 32) to the sum of DC voltages of the first DC voltage source (5, 25, 35) and the second DC voltage source (8, 10, 28, 38) is smaller than the ratio of the on-voltage of the non-Si semiconductor switching devices (6, 26, 36) to the DC voltage of the second DC voltage source (8, 10, 28, 38).