Stable solid preparation, comprising as an effective ingredient a 4,5-epoxymorphinan derivative represented by the general formula (I): in which a double line formed by a dashed line and a solid line represents a double bond or a single bond； R1 represents an alkyl having 1 to 5 carbon atoms, a cycloalkylalkyl having 4 to 7 carbon atoms, a cycloalkenyl alkyl having 5 to 7 carbon atoms, an aryl having 6 to 12 carbon atoms, an aralkyl having 7 to 13 carbon atoms, an alkenyl having 4 to 7 carbon atoms, an allyl, a furan-2-ylalkyl having 1 to 5 carbon atoms or a thiophene-2-ylalkyl that it has 1 to 5 carbon atoms； R2 represents hydrogen, hydroxy, nitro, an alkanoyloxy having 1 to 5 carbon atoms, an alkoxy having 1 to 5 carbon atoms, an alkyl having 1 to 5 carbon atoms or -NR7R8； R7 represents hydrogen or an alkyl having 1 to 5 carbon atoms； R8 represents hydrogen, an alkyl having 1 to 5 carbon atoms or -C (= O) R9-； R9 represents hydrogen, phenyl or an alkyl having 1 to 5 carbon atoms； R3 represents hydrogen, hydroxy, an alkanoyloxy having 1 to 5 carbon atoms or an alkoxy having 1 to 5 carbon atoms； A represents -N (R4) C (= X) -, -N (R4) C (= X) Y-, -N (R4) - or -N (R4) SO2-, where X and Y each independently represent NR4, S or O, and R4 represents hydrogen, a linear or branched alkyl having 1 to 5 carbon atoms or an aryl having 6 to 12 carbon atoms, and the R4 of the formulas may be the same or different； B represents (i) a valence bond, (ii) a linear or branched alkylene having 1 to 14 carbon atoms, which may be substituted, at least, with one or more substituents selected from the group consisting of an alkoxy that it has 1 to 5 carbon atoms, an alkanoyloxy having 1 to 5 carbon atoms, hydroxy, fluorine, chlorine, bromine, iodine, amino, nitro, cyano, trifluoromethyl, trifluoromethoxy and phenoxy, in which 1 to 3 alkylene methylene groups (ii) may be substituted with carbonyl groups, (iii) a linear or branched unsaturated acyclic hydrocarbon containing 1 to 3 double
