1. An image coding method for coding an image on a block-by-block basis, the method comprising: calculating a disparity motion vector predictor for predicting a motion vector of a current block to be coded, from a motion vector of a disparity block that is a block having a relationship of disparity with the current block and located at a position corresponding to a position of the current block; selecting a motion vector predictor for use in prediction of the motion vector of the current block, from among one or more motion vector predictor candidates including the disparity motion vector predictor; and coding (i) identification information corresponding to the motion vector predictor selected from among the one or more motion vector predictor candidates and (ii) a motion vector difference that is a difference between the motion vector of the current block and the motion vector predictor, wherein in the coding, when the motion vector of the disparity block refers to a field having a relationship of same parity with the disparity block, a bitstream shorter than a bitstream of the case where the motion vector of the disparity block refers to a field having a relationship of disparity with the disparity block is allocated to identification information corresponding to the disparity motion vector predictor, to code the identification information corresponding to the disparity motion vector predictor.