To provide a composition for polylactic acid-based resin moisture-proof coating, having excellent moisture barrier properties, transparency and adhesion to the polylactic acid-based resin.

The composition contains (A) 100 pts.wt. of an olefin/,-unsaturated carboxylic acid-based copolymer and (B) 1-100 pts.wt. of a substituted or unsubstituted styrene or its derivative/,-unsaturated carboxylic acid-based copolymer, and optionally (C) 1-100 pts.wt. of a wax-based resin and (D) 1-50 pts.wt. of an inorganic plate-like particle.