An image forming apparatus, includes a developing device developing an electrostatic latent image formed on an image bearing member. The developing device includes a developer bearing member having a developing sleeve and a magnet, with the developing sleeve being rotatable in the direction opposite to the rotational direction of the image bearing member, the magnet being fixed in the developing sleeve, and grooves extending in the axial direction being provided on a surface of the developing sleeve. An angle α between a wall surface of the grooves at an upstream side in the rotational direction of the developing sleeve and the direction perpendicular to the surface of the developing sleeve is greater than an angle γ of a magnetic brush of the developer formed at a closest portion between the image bearing member and the developer bearing member on an outermost surface of the developing sleeve.