A picture decoding method for decoding a current block included in a current picture in direct mode, the picture decoding method comprising: specifying a co-located block which is a block included in a second picture that is different from the current picture, the co-located block being located in the second picture at the same position that the current block is located in the current picture; determining a first motion vector (MV22') and a second motion vector (MV24') of the current block for performing motion compensation on the current block, using a third motion vector which is a motion vector of the co-located block; generating a first predictive image of the current block using the first motion vector (MV22') of the current block and a second predictive image of the current block using the second motion vector (MV24') of the current block; generating a predictive image of the current block based on the first predictive image and the second predictive image; decoding a coded difference image of the current block to obtain a decoded difference image of the current block; and reconstructing the current block by adding the decoded difference image of the current block and the predictive image of the current block, wherein the co-located block is motion-compensated using a first motion vector corresponding to a first reference picture of the co-located block, and the first motion vector (MV22') of the current block refers to the reference picture (P22, P21) referred to by the third motion vector of the co-located block, the second motion vector (MV24') of the current block refers to the second picture that is different from the current picture, and the picture decoding method being characterized in that the co-located block is motion-compensated using also a second motion vector corresponding to a second reference picture of the co-located block, and in the case where the first and second reference pictures (P22, P21) of the co-located block are both stored in a long-term picture buffer, (i) the third motion vector is determined to be equal to one of the first and second motion vectors (MV22, MV21) of the co-located block, and (ii) the first motion vector (MV22') of the current block is determined to be equal to the third motion vector, and (iii) the second motion vector (MV24') of the current block is determined to be a value of 0. specifying a co-located block which is a block included in a second picture that is different from the current picture, the co-located block being located in the second picture at the same position that the current block is located in the current picture; determining a first motion vector (MV22') and a second motion vector (MV24') of the current block for performing motion compensation on the current block, using a third motion vector which is a motion vector of the co-located block; generating a first predictive image of the current block using the first motion vector (MV22') of the current block and a second predictive image of the current block using the second motion vector (MV24') of the current block; generating a predictive image of the current block based on the first predictive image and the second predictive image; decoding a coded difference image of the current block to obtain a decoded difference image of the current block; and reconstructing the current block by adding the decoded difference image of the current block and the predictive image of the current block, wherein the co-located block is motion-compensated using a first motion vector corresponding to a first reference picture of the co-located block, and the first motion vector (MV22') of the current block refers to the reference picture (P22, P21) referred to by the third motion vector of the co-located block, the second motion vector (MV24') of the current block refers to the second picture that is different from the current picture, and the picture decoding method being characterized in that the co-located block is motion-compensated using also a second motion vector corresponding to a second reference picture of the co-located block, and in the case where the first and second reference pictures (P22, P21) of the co-located block are both stored in a long-term picture buffer, (i) the third motion vector is determined to be equal to one of the first and second motion vectors (MV22, MV21) of the co-located block, and (ii) the first motion vector (MV22') of the current block is determined to be equal to the third motion vector, and (iii) the second motion vector (MV24') of the current block is determined to be a value of 0.