An image forming apparatus including (a) a .gamma. conversion unit having a .gamma. conversion table .gamma..alpha..sub.i of a first one Vcont.alpha. of a designation development contrast in a case that a development contrast correction amount .DELTA.Vcont1 is a first value, and a .gamma. conversion table .gamma..beta..sub.i, different from the .gamma. conversion table .gamma..alpha..sub.i, of a second one Vcont.beta., different from the first one Vcont.alpha., of the designation development contrast in a case that the development contrast correction amount .DELTA.Vcont1 is a second value different from the first value, and (b) an arithmetic operation unit for calculating a .gamma. conversion table .gamma.Now.sub.i of a third one VcontNow of the designation development contrast in a case that the development contrast correction amount .DELTA.Vcont1 is a third value, based on a formula: .gamma.Now.sub.i=.gamma..alpha..sub.i+(.gamma..beta..sub.i-.gamma..alpha.- .sub.i).times.(Vcont.alpha.-VcontNow/(Vcont.alpha.-Vcont.beta.), wherein the subscript i is a value of an output density signal in the .gamma. conversion table. The .gamma. conversion unit conducts the .gamma. conversion of the third one VcontNow of the designation development contrast, based on the .gamma. conversion table .gamma.Now.sub.I calculated by the arithmetic operation unit.