An image forming apparatus includes an image carrier configured to carry an electrostatic latent image, a toner carrier configured to carry a toner and develop the electrostatic latent image, a switching member configured to perform a switching operation between a contact state where the toner carrier contacts the image carrier and a separation state where the toner carrier is separated from the image carrier, a first electrode member, a second electrode member arranged such that the electrostatic capacity between the first and second electrode members in the contact state is different from the electrostatic capacity therebetween in the separation state, a detection device configured to detect the electrostatic capacity between the first and second electrode members.