1. An image encoding apparatus comprising: a prediction preparing section which prepares a prediction for each intra-prediction mode by using at least ones of pixel signals of pixels lined horizontally in an upper end of an encoding target block and pixel signals of pixels lined vertically in a left end of the encoding target block among pixel signals of the encoding target block; and a prediction mode derivation section which executes an intra-prediction operation of the encoding target block by using an image of the encoding target block in an encoding target image and the prediction prepared by the prediction preparing section.