To suitably detect a color of test object from two or more kinds of candidate colors of a test object even when two or more kinds of colors of the test object having a predetermined color change permittable width are overlapped as the candidate colors of the test object.

This device has a color detection part 11 for detecting the presence of a candidate color of the test object having a predetermined color change permittable width from various component colors of R, G and G values of a color image with respect to a two or more kinds of candidate colors of the test object, and a binarization part 12 for detecting the presence of the color of the test object consisting of at least one of the candidate colors of the test object.