A developer for an electrophotographic tandem image forming method is provided that contains a toner; and a carrier, wherein the toner has a shape factor SF-1 of from 120 to 160, an average circularity of form 0.93 to 0.98, a weight-average particle diameter (D4) of from 3.0 to 8.0 .mu.m, and a ratio (D4/Dn) of the weight-average particle diameter (D4) to a number-average particle diameter (Dn) of from 1.01 to 1.20, and wherein the carrier is almost a spherical ferrite coated with a resin wherein alumina is dispersed, which has an average particle diameter of from 20 to 45 .mu.m and the following formula: (MgO)x(MnO)y(Fe.sub.2O.sub.3)z wherein x is from 1 to 5 mol %, y is from 5 to 55 mol % and z is from 45 to 55 mol %.