1. A moving picture coding device adapted to code moving pictures in units of blocks obtained by partitioning each picture, comprising: a spatial merge candidate generation unit configured to derive spatial merge candidates from a first predefined number of blocks neighboring a prediction block subject to coding; a temporal merge candidate generation unit configured to derive a temporal merge candidate from a block that exists at the same position as or near a prediction block subject to coding in a coded picture that is different from the prediction block subject to coding; a merge candidate addition unit configured to add the spatial merge candidates and the temporal merge candidates to a merge candidate list; a coding information selection unit configured to select a merge candidate from the merge candidates added to the merge candidate list; a motion compensation prediction unit configured to perform inter prediction of the prediction block subject to coding by the merge candidate thus selected; a first bitstream coding unit configured to set the number of merge candidates; and a second bitstream coding unit configured to code information indicating indices of the merge candidates, wherein the second bitstream coding unit derives the indices of the merge candidates based on the number of the merge candidates; and the spatial merge candidate generation unit stops deriving the spatial merge candidates when the number of the derived spatial merge candidates reaches a second predefined number smaller than the first predefined number.