When an output unit to produce output is specified through an instruction terminal 11 and original data is input to a color proof generation section 12, a color conversion section 13 acquires a color conversion parameter corresponding to the specified output unit from a color conversion information storage section 14 and performs color conversion processing for the original data so as to accomplish precise color reproduction in the specified output unit. A rasterizing section 15 expands the original data after undergoing the color conversion processing into raster data while using an enormous number of fonts in a font storage section 16. The raster data provided by the rasterizing section 15 is transmitted from a communication section 17 through a network 4 to the specified output unit. If a remote system 2 or 3, which receives the raster data, prints out on output unit 21 or 31, a color proof whose color is reproduced precisely can be provided.