A solid preparation includes a 4,5-epoxymorphinan derivative or a pharmaceutically acceptable acid addition salt thereof, which is stable to light even without light shielding coating. The solid preparation includes an active ingredient composed of a 4,5-epoxymorphinan derivative or a pharmaceutically acceptable acid addition salt thereof, and one or more stabilizing agents selected from the group consisting of n-propyl gallate, sodium hydrogensulfite, dibutylhydroxytoluene, butylhydroxyanisole, tocopherol and D-isoascorbic acid, wherein the amount of the above active ingredient is 0.00001 to 0.01% by weight of the solid preparation, and the amount of the above stabilizing agent is 0.005 to 5% by weight of the solid preparation.
