An electronic endoscope signal-processing device is provided that includes a gradation compensation processor. The gradation compensation processor compensates for R, G and B gradations by controlling R, G and B tone curves defining relationship between input values and output values of each of the R, G and B signals. The R tone curve is shaped so as to squash the output values of the R signal when the R signal input values are in a relatively low range and to expand the output values when the input values are in a relatively high range. The G and B tone curves are shaped so squash the output value of the respective signals when the input signals are in high or low ranges, and the G tone curve and the B tone curve are identical.
