Provided is an output inverter for single phase which can perform high precision current detection with a small number of components, and its output current detection method. A first current detector (6) is arranged between the DC power supply positive electrode P side of a first arm (8) and a parallel connection (1), a second current detector (7) is arranged between the DC power supply negative electrode N side of a second arm (9) and a parallel connection (4), a current in first reflux mode is detected by a first current detector (6), a current in second reflux mode is detected by a second current detector (7), and the output current is detected based on the output signals from the first current detector (6) and the second current detector (7).