To provide a single-phase converter which can reduce harmonics components of an input current for the entire region of a load current.

This single-phase converter comprises a rectifier for full-wave rectification of single-phase alternate current, a DC reactor connected at one terminal to one terminal of output side of the rectifier, a switching element connected between the other terminal of the DC reactor and the other terminal on the output side of the rectifier, a reverse blocking diode connected to one terminal of the switching element, a smoothing capacitor connected between the output side of the reverse blocking diode and the other terminal of the switching element, a current detector for detecting an AC input current, and an active control means for controlling the switching element. Therefore, in this single-phase converter, the switching element starts to become conductive at the zero-cross point of the single-phase AC voltage, and the conductive state of the switching element is completed after the passage of time which depends on an amplitude of the AC input current detected with the current detector.