The test image is formed in accordance with input data in which a plurality of recording elements selected every N (an integer of 1 or more) pieces in a projected recording element group is indicated as a first recording element and a recording element that is not selected as the first recording element is indicated as a second recording element, the input data allowing: a first-stage pattern to be formed in a recording area of the second recording element in accordance with a second input gradation value; a recording position in the second direction to be sequentially changed; and the first recording element and the second recording element to be sequentially switched to form a second-stage pattern to an (N+1)-th-stage pattern.