A developing apparatus includes: a developing sleeve that carries a mono-component developer; and a developing blade that abuts on the sleeve to regulate a layer thickness of the developer on the sleeve, wherein surface roughness parameters of the sleeve satisfy: 3.0.ltoreq.Rpk.ltoreq.9.0; and 2.ltoreq.Pc2.ltoreq.10. At an abutment portion between the sleeve and the blade, surface roughness parameters of the blade satisfy: 0.030.ltoreq.Sm.ltoreq.0.170; and 0.10.ltoreq.Rvk.times.(100-Mr2)/100.ltoreq.1.30, where Sm is a mean spacing of profile irregularities [mm]; Rpk is an initial wear height [.mu.m]; Rvk is an oil retaining depth [.mu.m]; Mr2 is a profile bearing length ratio 2 [%]; and Pc2 denotes the number of profile peaks having a height larger than a count level from a center line per the evaluation length of 1 mm.