An image forming apparatus comprises a developer carrier (101) for developing an electrostatic latent image by supplying an image carrier with developer inside a developer container (100); an electrode member (104) opposing the developer carrier (101) via a space accommodating the developer; an inverter (301); a transformer (302) for transforming an AC voltage from the inverter (301); a rectifying circuit (303) for rectifying the output of the transformer and generating a DC voltage for image formation; a DC voltage applying unit (306) for applying the AC voltage, which is output from the transformer, to the electrode member (104); and a developer remaining-amount detection unit (305) for detecting amount of developer remaining inside the developer container (100) based upon electrostatic capacitance between the developer carrier (101) and electrode member (104).