to provide an image forming method that includes supplying a toner to a developing roller using a toner supplying roller , and forming an image by the use of a one - component developer , wherein the toner supplying roller contains a polyurethane foam and is 5 mm to 12 mm in diameter , the polyurethane foam has an repulsion force of 100 g / mm to 400 g / mm , and the average cell diameter , or dc , of the polyurethane foam and the volume average particle diameter , or dt , of the toner satisfy the following mathematical expressions : 4 ≦ dt ≦ 10 30 dt + 50 ≦ dc ≦ 30 dt + 300 where dt and dc are in micrometer .