To suppress the whitening of a heat-sealed part of a packaging film coated with a vinylidene chloride polymer even by treating the heat-sealed film with hot water.

A film having high gas-barrierness is produced by coating a substrate film with a coating agent containing a vinylidene chloride polymer and a modified wax having introduced functional groups selected from carboxyl group, acid anhydride group, ester group and hydroxyl group. The vinylidene chloride polymer includes a crystalline vinylidene chloride polymer soluble in an organic solvent. The content of the modified wax is about 0.01-10 pts.wt. based on 100 pts.wt. of the vinylidene chloride polymer. The film may have a heat-sealing layer.