The present invention relates to a packaging material for an oral soft capsule formulation containing dutasteride, wherein the packaging material has a water vapor transmission rate (WVTR) of 0.005-0.75 g/m2/day at relative humidity of 90% at 38癈. The packaging material, even when an oral soft capsule formulation containing dutasteride is stored for a long period of time, causes no changes in formulation properties and exhibits excellent stability against the disintegration of a formulation and the dissolution of a drug. Therefore, the packaging material can be favorably used as a packaging material for an oral soft capsule formulation containing dutasteride.