A developing device includes a developer container for accommodating one component magnetic toner; a rotatable toner carrying member, faced to an image bearing member for bearing an electrostatic image to form a developing zone therebetween, for carrying the toner in the container; a magnet member in the toner carrying member; a regulating member, elastically urged to the toner carrying member to form a nip therebetween, for regulating a toner layer thickness on the toner carrying member; wherein the magnet member has a magnetic pole, upstream of the nip with respect to a movement direction of the toner carrying member, for supplying the toner in the container to the toner carrying member, and wherein the magnet member does not generate a magnetic field effective for chain erection of the toner in a range from an upstream end of the nip to a downstream end of the developing zone.