PURPOSE: To reduce the quantity of a circuit and a cost by selecting an input source to a gamma correction means and an output destination of a gamma correction coefficient after gamma correction depending on each operation and sharing with the common gamma correction means for the gamma correction at the time of each operation such as transmission, reception and copying.

CONSTITUTION: First - third selectors 30, 31, 37 switch an input source, an output destination and each gamma correction coefficient of a gamma correction section 32 based on a control signal in each operation such as transmission, reception and copying of the equipment. Thus, a correction section 32 before each operation inputs and writes one of read/display/copying use gamma correction coefficients 34-36 depending on each operation kind from a correction coefficient memory 33. That is, according to a control signal from an input terminal 38, a reception system 24 or an image sensor 21 and a display device 25 or a transmission system 22 and furthermore a corresponding coefficient are selected respectively and the density is corrected and each operation is executed. Thus, the common use correction section 32 is used to reduce a circuit quantity and a cost.