A moving picture coding apparatus includes a motion estimation unit (101) for performing motion estimation by fixing the one of two reference pictures as a reference picture indicated by an inputted default reference picture number DefRefNo and a variable length coding unit (107) for performing variable length coding on coded residual data ERes, a prediction type PredType, a reference picture number RefNo2 and motion vectors MV1, MV2 on a block-by-block basis, and outputting them as coded moving picture data Str.For use in making the interpolation prediction of a plurality of reference pictures, a moving image coding device comprises a moving prediction unit (101) that makes movement prediction with one of two reference pictures fixed by selected as indicated by a received default reference picture number DefRefNo; and a variable-length coding unit (107) that performs variable-length coding of residual coding data ERes, by-prediction type PredType, reference picture number RefNo2, and motion vectors MV1 and MV2 for every block, and of the default reference picture number DefRefNo for every picture, to output the data as moving image coded data Str.