A developing apparatus includes a developer carrying member for carrying a developer including one component magnetic toner to develop an electrostatic image formed on an image bearing member. The developer carrying member includes an elastic member contactable to the image bearing member; magnetic field generating means, for attracting the developer to the developer carrying member, and a regulating member for regulating an amount of the developer carried on the developer carrying member. The developer is regulated by the regulating member and applied on the developer carrying member at 5-16 g/mk.sup.2. At a position where the regulating member is contacted to the developer carrying member, a magnetic flux density B generated by the magnetic field generating means, and a component Br of the magnetic flux density B normal to a surface of the developer carrying member, satisfy, |Br|/|B|.ltoreq.0.5.