An image decoding apparatus (31) includes a CT information decoding unit (10) configured, in each coding tree, to decode a constraint flag indicating whether or not to constrain decoding a prediction unit, and a CU decoding unit (20) configured, in the coding tree, to decode a prediction unit in a coding node to be decoded first and to not decode a prediction unit in another coding node, in a case that the constraint flag indicates constraint of decoding the prediction unit. According to the present invention, it is possible to reduce a coding amount of PU and complexity of coding/decoding an image while maintaining a split with a high degree of freedom by CT split (QT split and BT split).