Image forming apparatus

An image forming apparatus, comprising:

• an image carrier configured by a positively charged single-layer electrophotographic photosensitive body;
• a charging device which is based on a contact charging method for charging a circumferential surface of the image carrier while making contact with the circumferential surface of the image carrier;
• a developing roller disposed to oppose the image carrier and carrying and conveying toner on the circumferential surface;
• a magnetic roller disposed to oppose the developing roller, the magnetic roller carrying and conveying a two-component developer including the toner on the circumferential surface;
• and
• a voltage application unit which applies a developing bias to the developing roller, wherein
• the frequency of an AC component of the developing bias applied by the voltage application unit is 2.6 to 4.2 kHz, and
• the charging device performs charging so as to satisfy Formula (I) below:
• 75X+240≦Y≦600 (I)
• where, X indicates the frequency (kHz) of the AC component of the developing bias voltage and Y indicates the surface potential (V) of the image carrier.