PURPOSE: To obtain a correct evaluation result by evaluating both gradation reproduction and edge reproduction.

CONSTITUTION: In a 2×2 picture element array taking-out processing 20, the 2×2 picture element array of an N(2<N) value pseudo multilevel picture A and the 2×2 picture element array of the original picture B are taken-out. In a differnence calculation processing 30, difference between the total sum of the multilevel value of a pseudo multilevel picture four picture elements and the total sum of the multilevel value of the original picture four picture elements to which a coordinate corresponds is calculated by an array unit. In an evaluation expression calculation processing 40, the relation of the picture elements is calculated, a prescribed evaluation expression is calculated and it is judged that the quality of the N value pseudo multilevel picture A is high when the result of the evaluation expression is smaller.