<p>In a video coding device the prediction error value calculated by a motion estimating portion 18 is used for selecting the frame or field orthogonal transform coding mode. The frame prediction error value EFr and the field prediction error value EFi are calculated by the motion estimating portion 18 and entered into a comparator 21 of an orthogonal transform mode selecting portion 6 which in turn compares them with each other and generates an orthogonal transform mode selecting signal TC. The use of the prediction error values for selecting the orthogonal transform mode makes it possible to reduce the size of the necessary hardware and saves much time of data processing necessary for judgment of the orthogonal transform mode selection. &lt;MATH&gt;</p>