In a correction processing that corrects a color deviation caused by output characteristic variations among print heads of a printing apparatus, the printing apparatus prints a test pattern that allows accurate detection of the color deviation by a visual check. More specifically, each of the patches in the test pattern is made up of two areas placed adjacent to each other. One of the two areas (upper area) is used as a test area for detecting the degree of the color deviation. Of the gradation values of C, M and Y, which make up the patch print data, the gradation values of C and M are changed among the patches making up the test pattern. The other area is used as a reference area printed with an achromatic color that represents a reference gradation value for the deviation detection. The gradation values of C, M, Y and K are determined so that a spatial frequency of dots formed in the reference area of each patch is close to the spatial frequency of the associated test area.