PURPOSE: To stabilize a drug active constituent which is easily decomposed by light, e.g. nifedipine contained in the soft capsule, by coating the surface of a film of a soft capsule with a very small amount of a dyestuff film of Food Yellow No.4 and/or Food Yellow No.5.

CONSTITUTION: The surface of a gelatin layer of a soft capsule, i.e. only the surface to be in contact with air, is coated with 0.05W1.0wt%, based on the total amount of capsule film, dyestuff film of Food Yellow No.4 and/or Food Yellow No.5 to give the titled molded capsule. According to the method, a drug, e.g. nifedipine, unstable to light can be stabilized by using a much smaller amount of the dyestuff than in the method for incorporating the dyestuff in the total film. The soft capsule containing the nifedipine is introduced into a pan for sugar coating or film coating, and a solution of the dyestuff is poured or sprayed on the soft capsule while rotating the capsule. An additive may be added to the solution of the dyestuff to improve the appearance or efficiency of the coloring operation.