To estimate an image quality deterioration level at a high accuracy. An image quality deterioration level is estimated by judging whether image quality deterioration is suppressed or not by error concealment processing when decoding is not correctly performed, based on information obtained in decoding processing. When it is judged that error concealment is effectively operated, it is estimated that deterioration of an image quality even in an image region not correctly decoded is small. When it is estimated that error concealment is not effectively operated, it is estimated that image deterioration is heavy.