Upon setting of a halftone process of an initial setting, there is such a problem that graininess deteriorates due to an aging change or an environmental change. To solve this problem, an image processing apparatus executes a halftone process on a test image for tone correction and prints the processed test image; forms a tone correction table in accordance with read values from the printed test image; obtains graininess from a read value of a low density portion of a tone correction patch of the test image for the tone correction; discriminates whether the obtained graininess exceeds a predetermined reference level; and changes a setting of the halftone process so as to reduce the graininess when it is discriminated that the obtained graininess exceeds the predetermined reference level.