An image decoding apparatus for decoding a picture for each of coding tree units, the image decoding apparatus comprising: a coding node information decoder configured to perform a binary tree split possibility determination based on a width of a target node, a height of the target node, a minimum size of a coding unit, a maximum size of the coding unit and a level of hierarchy of the target node and determine whether or not a binary tree split is possible, perform a ternary tree split possibility determination based on a width of the target node, a height of the target node, a minimum size of a coding unit, a maximum size of the coding unit and a level of hierarchy of the target node and determine whether or not a ternary tree split is possible, determine whether or not decoding of a partition tree split flag is required based on the binary tree split possibility determination and the ternary tree split possibility determination, wherein the partition tree split flag indicates whether or not the target node is to be split by the binary tree split or the ternary tree split, decode the partition tree split flag only in a case that a split by either the binary tree split or the ternary tree split is possible, determine whether or not decoding of a split direction flag is required based on the partition tree split flag, wherein the split direction flag indicates a split direction, decode the split direction flag only in a case that the partition tree split flag indicates that the target node is to be split, determine whether or not decoding of a split mode selection flag is required based on the binary tree split possibility determination and the ternary tree split possibility determination, wherein the split mode selection flag indicates a split method which is the binary tree split or the ternary tree split, decode the split mode selection flag only in a case that the binary tree split and the ternary tree split are both possible, and split the target node of the coding tree units by the binary tree split or the ternary tree split based on the split direction flag and the split mode selection flag, wherein the coding node information decoder further determines additional conditions of the binary tree split possibility determination, wherein the coding node information decoder in a case that the target node is a middle node of three nodes obtained by performing ternary tree split on an immediately higher node, prohibits split of the target node by binary tree split in a direction identical to a direction of the ternary tree split performed on the immediately higher node, and in a case that the binary tree split is prohibited, does not decode the split mode selection flag and sets the split mode selection flag to a value indicating the ternary tree split. a coding node information decoder configured to perform a binary tree split possibility determination based on a width of a target node, a height of the target node, a minimum size of a coding unit, a maximum size of the coding unit and a level of hierarchy of the target node and determine whether or not a binary tree split is possible, perform a ternary tree split possibility determination based on a width of the target node, a height of the target node, a minimum size of a coding unit, a maximum size of the coding unit and a level of hierarchy of the target node and determine whether or not a ternary tree split is possible, determine whether or not decoding of a partition tree split flag is required based on the binary tree split possibility determination and the ternary tree split possibility determination, wherein the partition tree split flag indicates whether or not the target node is to be split by the binary tree split or the ternary tree split, decode the partition tree split flag only in a case that a split by either the binary tree split or the ternary tree split is possible, determine whether or not decoding of a split direction flag is required based on the partition tree split flag, wherein the split direction flag indicates a split direction, decode the split direction flag only in a case that the partition tree split flag indicates that the target node is to be split, determine whether or not decoding of a split mode selection flag is required based on the binary tree split possibility determination and the ternary tree split possibility determination, wherein the split mode selection flag indicates a split method which is the binary tree split or the ternary tree split, decode the split mode selection flag only in a case that the binary tree split and the ternary tree split are both possible, and split the target node of the coding tree units by the binary tree split or the ternary tree split based on the split direction flag and the split mode selection flag, wherein the coding node information decoder further determines additional conditions of the binary tree split possibility determination, wherein the coding node information decoder in a case that the target node is a middle node of three nodes obtained by performing ternary tree split on an immediately higher node, prohibits split of the target node by binary tree split in a direction identical to a direction of the ternary tree split performed on the immediately higher node, and in a case that the binary tree split is prohibited, does not decode the split mode selection flag and sets the split mode selection flag to a value indicating the ternary tree split.