1. An image forming method comprising: an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier; a developing step of forming a toner image of the electrostatic latent image on the electrostatic latent image carrier; a transfer step of transferring the toner image to an intermediate transfer member by forming an electric field between the electrostatic latent image carrier and the intermediate transfer member, and; a first detecting step of detecting an image density of an image that is transferred using a predetermined reference electric field; a second detecting step of detecting an image density of the image that is transferred using an electric field that is smaller or greater than the reference electric field; and a processing step of processing a degraded toner based on the image density detected by each of the first detecting step and the second detecting step.