A piecewise linear processing device applies different amplification rates according to a general environment and a low luminance environment where much noise exists. The piecewise linear processing device includes a knee point storing unit configured to store a user's default setting value and low luminance setting value; a luminance detecting unit configured to detect a noisy environment to output a current luminance information signal and a maximum luminance information signal; an adaptive knee point supply unit configured to receive the default setting value, the low luminance setting value, the current luminance information signal, and the maximum luminance information signal to supply a adjusted adaptive knee point according to a degree of noise; and a piecewise linear processing unit configured to apply a section amplification rate to an input data on the basis of a region corresponding to the adaptive knee point.