Herein disclosed is an inverter device which includes two or more groups of unit switching circuits connected in parallel with a d.c. power source and each having gate turn-off thyristors connected in series with each other. Further inclusive are current balancing reactors, which are respectively connected between the series nodes of the gate turn-off thyristors of the respective groups, and a.c. output terminals respectively leading out from intermediate points of the aforementioned reactors.