A morphinan derivative represented by the following general formula: (wherein, R 1 represents hydrogen, C 1-6 alkyl, C 3-6 cycloalkyl, C 6-10 aryl, heteroaryl (containing 1 to 4 heteroatoms selected from N, O and S as a ring-constituting atom), aralkyl (the aryl moiety has 6 to 10 carbon atoms, and the alkylene moiety has 1 to 5 carbon atoms), heteroarylalkyl (the heteroaryl contains 1 to 4 heteroatoms selected from N, O and S as a ring-constituting atom, and the alkylene moiety has 1 to 5 carbon atoms), cycloalkylalkyl (the cycloalkyl moiety has 3 to 6 carbon atoms, and the alkylene moiety has 1 to 5 carbon atoms), C 2-6 alkenyl, arylalkenyl (the aryl moiety has 6 to 10 carbon atoms, and the alkenyl moiety has 2 to 6 carbon atoms), heteroarylalkenyl (the heteroaryl contains 1 to 4 heteroatoms selected from N, O and S as a ring-constituting atom, and the alkenyl moiety has 2 to 6 carbon atoms), cycloalkylalkenyl (the cycloalkyl moiety has 3 to 6 carbon atoms, and the alkenyl moiety has 2 to 6 carbon atoms), C 4-6 cycloalkenyl, cycloalkenylalkyl (the cycloalkenyl moiety has 4 to 6 carbon atoms, and the alkylene moiety has 1 to 5 carbon atoms), or cycloalkenylalkenyl (the cycloalkenyl moiety has 4 to 6 carbon atoms, and the alkenyl moiety has 2 to 6 carbon atoms), R 2 and R 3, which are the same or different, represent hydrogen, hydroxy, cyano, carbamoyl, C 1-6 alkoxy, C 6-10 aryloxy, or C 1-6 alkanoyloxy, R 4 and R 5, which are the same or different, represent hydrogen, C 1-6 alkyl, C 3-6 cycloalkyl, C 6-10 aryl, cycloalkylalkyl (the cycloalkyl moiety has 3 to 6 carbon atoms, and the alkylene moiety has 1 to 5 carbon atoms), aralkyl (the aryl moiety has 6 to 10 carbon atoms, and the alkylene moiety has 1 to 5 carbon atoms), or heteroarylalkyl (the heteroaryl contains 1 to 4 heteroatoms selected from N, O and S as a ring-constituting atom, and the alkylene moiety has 1 to 5 carbon atoms), or R 5 and R 4 may combine together to form a 4- to 7-membered ring (which may contain a heteroatom selected from N, O and S as a ring-constituting atom other than the N atom to which R 5 binds) together with the nitrogen atom to which R 5 binds, R 6 represents hydrogen, hydroxy, C 1-6 alkyl, C 3-6 cycloalkyl, C 6-10 aryl, cycloalkylalkyl (the cycloalkyl moiety has 3 to 6 carbon atoms, and the alkylene moiety has 1 to 5 carbon atoms), aralkyl (the aryl moiety has 6 to 10 carbon atoms, and the alkylene moiety has 1 to 5 carbon atoms), or heteroarylalkyl (the heteroaryl contains 1 to 4 heteroatoms selected from N, O and S as a ring-constituting atom, and the alkylene moiety has 1 to 5 carbon atoms), or R 6 and R 5 may combine together to form a 4- to 7-membered ring (which may contain a heteroatom selected from N, O and S as a ring-constituting atom other than the N atom to which R 5 binds) together with the N atom to which R 5 binds, X represents O or CH 2, Y represents C=O, C(=O)O, C(=O)NR 7, SO 2, or a bond, wherein R 7 represents hydrogen, C 1-6 alkyl, aralkyl (the aryl moiety has 6 to 10 carbon atoms, and the alkylene moiety has 1 to 5 carbon atoms), heteroarylalkyl (the heteroaryl contains 1 to 4 heteroatoms selected from N, O and S as a ring-constituting atom, and the alkylene moiety has 1 to 5 carbon atoms), or cycloalkylalkyl (the cycloalkyl moiety has 3 to 6 carbon atoms, and the alkylene moiety has 1 to 5 carbon atoms), or the N atom to which R 7 binds and R 1 may combine together to form a 4- to 7-membered ring (which may contain a heteroatom selected from N, O and S as a ring-constituting atom other than the N atom to which R 7 binds), and m and n, which are the same or different, represent an integer of 0 to 2 (m and n are not 0 at the same time), wherein the C 1-6 alkyl regarding R 1, R 4, R 5 and R 6, the 4- to 7-membered ring formed by R 5 and R 6, and the 4- to 7-membered ring formed by R 5 and R 4 may be substituted with hydroxy group, and the aryl moiety of the C 6-10 aryl and the aralkyl (the aryl moiety has 6 to 10 carbon atoms, and the alkylene moiety has 1 to 5 carbon atoms) regarding R 1, and the heteroaryl moiety of the heteroaryl (containing 1 to 4 heteroatoms selected from N, O and S as a ring-constituting atom) and the heteroarylalkyl (the heteroaryl contains 1 to 4 heteroatoms selected from N, O and S as a ring-constituting atom, and the alkylene moiety has 1 to 5 carbon atoms) regarding R 1 may be substituted with at least one substituent selected from C 1-6 alkyl, C 1-6 alkoxy, C 1-6 alkanoyloxy, hydroxy, alkoxycarbonyl (the alkoxy moiety has 1 to 6 carbon atoms), carbamoyl, alkylcarbamoyl (the alkyl moiety has 1 to 6 carbon atoms), dialkylcarbamoyl (each alkyl moiety has 1 to 6 carbon atoms), halogen, nitro, cyano, C 1-6 alkyl substituted with 1 to 3 halogens, C 1-6 alkoxy substituted with 1 to 3 halogens, phenyl, heteroaryl (containing 1 to 4 heteroatoms selected from N, O and S as a ring-constituting atom), phenoxy, phenylalkyl (the alkyl moiety has 1 to 3 carbon atoms), methylenedioxy, and NR 8 R 9, wherein R 8 and R 9 independently represent hydrogen, C 1-6 alkyl, C 2-6 alkenyl, C 3-6 cycloalkyl, C 1-6 alkanoyl, or alkoxycarbonyl (the alkoxy moiety has 1 to 6 carbon atoms), or R 8 and R 9 may form, together with the N atom to which they bind, a 4- to 7-membered ring which may further contain a heteroatom selected from N, O and S), a tautomer or stereoisomer of the compound, or a pharmaceutically acceptable salt thereof, or a solvate thereof.