A power-factor correcting converter includes: a series circuit including a first higher-potential switch and a first lower-potential switch connected in series to each other; and another series circuit including a second higher-potential switch and a second lower-potential switch connected in series to each other. In a positive phase period of the input AC voltage, a control circuit turns off the second higher-potential switch, turns on the second lower-potential switch, and alternately turns on and off the first lower-potential switch as a master switch and the first higher-potential switch as a slave switch. In a negative phase period of the input AC voltage, the control circuit reverses the on/off operation and the master/slave relationship, and turns on and off only the master switch and turns off the slave switch when the absolute value of the input AC voltage is smaller than or equal to a predetermined value.