An image decoding method includes decoding encoded image data to generate a decoded image signal including a luma signal and a chroma signal. The method further includes scaling, when a reference field has a different parity from a current field for motion compensation and when the decoded image signal is in a format in which the number of chroma pixels is vertically different from the number of luma pixels, a chroma motion vector of the chroma signal according to an accuracy for a luma motion vector of the luma signal so that a reference frame will coincide in phase of the chroma signal with a current frame. The method also includes performing motion compensation of the decoded image signal using the scaled chroma motion vector according to the accuracy of the luma motion vector of the luma signal.