To perform, with a single circuit, decoding in association with various image encoding systems and improve universality, a coefficient selection processing section selects a DC coefficient and an AC coefficient of an adjacent block adjacent to a decoding target block, a coefficient arithmetic processing section applies arithmetic processing to the selected DC coefficient and AC coefficient, a coefficient comparison processing section calculates, based on the DC coefficient subjected to the arithmetic processing, inter-block correlations in horizontal and vertical directions, and a direction determination processing section determines a predicting method using the inter-block correlations. Further, a prediction processing section adds, using the determined predicting method, the DC coefficient and the AC coefficient subjected to the arithmetic processing to encoded data, and a controlling section controls, according to the encoded data, a selecting method, an arithmetic processing method, a determining method, and/or a prediction processing method.