A first dot pattern printed according to a result of quantization performed on a multi-valued grayscale value by using a first threshold matrix and a second dot pattern printed according to a result of quantization performed on multi-valued grayscale value by using a second threshold matrix are printed on a print medium in an overlapping manner. In order to generate the threshold matrices, a first initial pattern being a dot pattern corresponding to a first grayscale value and a second initial pattern being a dot pattern corresponding to a second grayscale value lower than the first grayscale value are generated for pixel regions of the first and second threshold matrices. Then, thresholds of the first and second threshold matrices are set such that dot patterns having continuity with the first and second initial patterns are obtained at grayscale values between the first and second grayscale values.