An encoding device includes: a memory; and a processor coupled to the memory and configured to: estimate a prediction value in a reference direction that is selected when intra prediction in an angle prediction mode is performed in a block to be processed on the basis of a value indicating a reference direction selected when the intra prediction in the angle prediction mode has been performed in an adjacent block adjacent to the block to be processed; and binarize the value indicating the reference direction selected when the intra prediction in the angle prediction mode has been performed in the block to be processed and perform arithmetic encoding for a comparison result between a value of a most significant bit of a binary signal and the prediction value.