An image forming apparatus includes an image bearing member; a charging device for electrically charging the image bearing member; a rotatable developer carrying member for carrying a developer to develop an electrostatic image formed on the image bearing member with the developer, the developer carrying member being supplied with a developing bias voltage including an AC voltage; non-rotatable magnetic field generating device, disposed inside the developer carrying member, for magnetically attracting the developer on the developer carrying member, wherein the developer carrying member has a surface elastic layer, and the developer carrying member is press-contacted to the image bearing member, and the developer is one component magnetic toner, and a maximum value of an absolute value of the developing bias voltage |V|max and a surface potential of the image bearing member charge by the charging device is Vd(V), satisfy, |V|max=|Vd|.