A developing device includes a developer support member and a developing blade having a curved portion abutting against the developer support member. When Rc represents a minimum curvature radius of the curved portion of the developing blade and R represents a curvature radius at an abutting point where the curved portion abuts against the developer support member, a ratio of R to Rc (R/Rc) meets the following relation. 1.0.ltoreq.R/Rc.ltoreq.1.2