A color separation apparatus comprising: a target value acquisition device which acquires target values of each colors to be reproduced in a printer when binary image data for each color material being necessary for forming dots of an image for each color material by the printer is created from continuous-tone image data; a dot threshold data candidate selection device (106, 108) which acquires candidates of dot threshold data including information on a threshold for each the dots for converting the continuous-tone image data for each color material into binary image data for each color material; a print profile acquisition device (106, 108) which acquires a print profile showing correspondence between a device signal value in the printer and a color system value for each of the candidates of dot threshold data; a device signal value candidate calculation device which calculates candidates of a device signal value for reproducing colors corresponding to the target values by the printer on the basis of the target values of the colors acquired by the target value acquisition device and the print profile; a simulation device which applies binary coded processing to the candidates of the device signal values by using the candidates of the dot threshold data to crate binary image date for each color material for each of the candidates, and simulates an image formed by the printer on a printed matter by superimposing binary image data for each the color material, the simulation device performing on-plate dot shape estimation processing for estimating shape and arrangement of dots to be formed on a printing plate of the printer and on-printed-matter dot shape estimation processing for estimating shape and arrangement of dots to be formed on the printed matter by the printing plate; a color evaluation value holding device which holds a color evaluation value showing a color difference between a device signal value and a color corresponding to the target value for each of the candidates of the device signal value; an image quality evaluation value calculation device which calculates an image quality evaluation value for each of the candidates of the device signal value on the basis of a result of simulation of the image to be formed on the printed matter; and a device signal value determination device (114, 118, 120) which determines dot threshold data for reproducing colors corresponding to the target values by the printer, from among the candidates of dot threshold data and device signal value for reproducing colors corresponding to the target values by the printer from among the candidates of device signal values, on the basis of the color evaluation value and the image quality evaluation value. a target value acquisition device which acquires target values of each colors to be reproduced in a printer when binary image data for each color material being necessary for forming dots of an image for each color material by the printer is created from continuous-tone image data; a dot threshold data candidate selection device (106, 108) which acquires candidates of dot threshold data including information on a threshold for each the dots for converting the continuous-tone image data for each color material into binary image data for each color material; a print profile acquisition device (106, 108) which acquires a print profile showing correspondence between a device signal value in the printer and a color system value for each of the candidates of dot threshold data; a device signal value candidate calculation device which calculates candidates of a device signal value for reproducing colors corresponding to the target values by the printer on the basis of the target values of the colors acquired by the target value acquisition device and the print profile; a simulation device which applies binary coded processing to the candidates of the device signal values by using the candidates of the dot threshold data to crate binary image date for each color material for each of the candidates, and simulates an image formed by the printer on a printed matter by superimposing binary image data for each the color material, the simulation device performing on-plate dot shape estimation processing for estimating shape and arrangement of dots to be formed on a printing plate of the printer and on-printed-matter dot shape estimation processing for estimating shape and arrangement of dots to be formed on the printed matter by the printing plate; a color evaluation value holding device which holds a color evaluation value showing a color difference between a device signal value and a color corresponding to the target value for each of the candidates of the device signal value; an image quality evaluation value calculation device which calculates an image quality evaluation value for each of the candidates of the device signal value on the basis of a result of simulation of the image to be formed on the printed matter; and a device signal value determination device (114, 118, 120) which determines dot threshold data for reproducing colors corresponding to the target values by the printer, from among the candidates of dot threshold data and device signal value for reproducing colors corresponding to the target values by the printer from among the candidates of device signal values, on the basis of the color evaluation value and the image quality evaluation value.