An image processing apparatus comprises positive and negative original input signal processing sections respectively converting positive and negative signals obtained by photoelectric scanning of positive and negative originals into positive density signals, and a color processing section for color-processing the positive density signals. The circuits used in the positive original input signal processing section are preferably all included as well in the negative original input signal processing section, so that common circuits may be employed for the two processing sections. This is similarly the case with the positive and negative image output sections. The apparatus also has a positive image output section for converting the output signal of the color processing section into a light amount control signal for a light source for reproducing a positive image, and a negative image output section for converting the output signal of the color processing section into a negative density signal and then into a light amount control signal for forming an intermediate negative so that a desired density is obtained on an ultimate printing photosensitive material when the intermediate negative is printed thereon. During processing in the negative original input signal processing section, a negative original density signal is converted into a density signal representing a corresponding positive image such that the weight ratio of the Y, M and C color signals is always 1:1:1 for a gray original.