PURPOSE: To uniform or adjust the tonal characteristics of plural color signals, and to realize an optimal white balance by providing a 7 correcting circuit having a KNEE characteristic and at least two variable gain amplifying circuits.

CONSTITUTION: Three primary color signals G, R, and B indicating picked-up object images are outputted from an image pickup device 10. A microcomputer 11 controls the gains of variable gain amplifier circuits 15 and 16 by using the data of a peak detection circuit 12 in order to temporarily adjust the white balance. The color signals G, R, and B inputted to a γ correcting circuit 40 are γ-corrected by an input/output characteristic curve having a KNEE curve at one part according to the sizes of the inputs, and outputted. The gains of the variable gain amplifier circuits 55 and 56 are set so that the tonal characteristics of the signals G, R, and B can be made coincident, and that differences between the black peak levels and the white peak levels can be made coincident.