A developing device including a toner support member for supporting toner on its surface, which is so provided as to confront an electrostatic latent image support member and a regulation member for forming a thin layer of the toner on the toner support member, which includes a curved member for pressing the toner support member and a support member for supporting the curved member such that an area S of a space satifies an equation: 0<S</=0.15 mm2 wherein the space is defined in a radial plane of the toner support member and the curved member and is bounded by the toner support member, the curve member and a line drawn in parallel with a normal extending through a point of contact between the toner support member and the curved member and spaced a radius of curvature of the curved member from the normal at an upstream side of the normal in a direction of rotation of the toner support member.
