In a two-component development system containing a toner and a carrier, an a-Si photosensitive member having a diameter of from 20 mm to 80 mm is used, the photosensitive member is electrostatically charged to have a surface potential of from 300 to 450 V (absolute value), and yellow, magenta, cyan and black toners are used each of which have a weight-average particle diameter of from 4.0 &mgr;m to 10.0 &mgr;m, and, under a condition that the carrier of the two-component developer has a 50% average particle diameter of from 10 &mgr;m to 80 &mgr;m and as image density (D0.5) measured usually after the toner is fixed once when the quantity of unfixed toner on a transfer medium, M/S, is 0.5 mg/cm2, have a coloring power of from 1.0 to 1.9, and in which the difference between a maximum value and a minimum value of D0.5 of yellow, magenta, cyan and black colors is form 0 to 0.5. This makes it possible to obtain high-quality images in a high image density and a superior color reproduction.