A developing device includes a rotatable developer carrying member for carrying a developer to develop an electrostatic image formed on an image bearing member with the developer; non-rotatable magnetic field generating means, disposed inside the developer carrying member, for magnetically attracting the developer on the developer carrying member; a regulating member for regulating an amount of the developer carried on the developer carrying member, wherein the developer carrying member is provided with a surface elastic layer, and the developer carrying member is press-contacted to the image bearing member, and wherein, the developer is an one component magnetic toner having an average circularity not less than 0.965, and an amount of the developer per unit area of the developer regulated by the regulating member is 5-14 g/m.sup.2, and an amount of electric charge thereof is 10-50 .mu.C/g.