To realize coincidence in color signal suitable for an observation state by detecting the observation states of an original image and a reproduction image and obtaining the degrees of adaptation states in observing the both pictures.

A scanner RGB signal is converted into a (X1, Y1 and Z1) signal in a color converting part 1. An observation condition correction processing part 5 converts a measured value (X1, Y1 and Z1) under a standard light source into (X1', Y1' and Z1') under an actual light source. The observation states are detected 8, an adaptation correcting part 9 executes a correction processing based on the adaptation degrees in accordance with the observation states and a correction value (X1", Y1" and Z1") is outputted. the color converting part 2 converts (X1", Y1" and Z1") into a monitor display signal RGB through the use of a color conversion parameter Pm so as to display it.