To prevent the inflow of a current from a distribution line to an inverter device in order to let it always output a high quality current of less distortion.

This device comprises two inverter parts 22, 23, an output transformer 29 and a controlling part 40. With an input side connected in parallel to a DC power supply (a solar cell 21), the inverter parts 22, 23 convert the DC power supply into an AC power supply of single-phase two-wire system. With the single-phase two-wire output of the inverter parts 23, 23 fed to each of primary windings 32, 33 and also with the middle tap and both ends 34a, 34b of a secondary winding 34 connected to a neutral line 12 and the rest two lines 13, 14 of a distribution line 11, the output transformer 29 forms an AC power supply of single-phase three-wire system by using the single-phase two- wire output of both inverter parts 22, 23 to share a power supply between a middle tape 35 and both ends 34a, 34b. Following the voltage between the neutral line 13 and the two lines 14, 15 to variably control the voltage of the single-phase two-wire output of the inverter parts 22, 23 independently, a controlling part 40 prevents the inflow of a current caused by the unbalanced voltage of the distribution line 11 to the output transformer 29.