A sterol derivative represented by the general formula:, wherein Y represents optionally substituted lower alkyl or optionally substituted lower alkenyl, X a and X b are the same or different, and represent a bond or -NR a - (wherein R a represents a hydrogen atom, optionally substituted lower alkyl, optionally substituted cycloalkyl, optionally substituted lower alkanoyl, or optionally substituted aroyl), R 1, R 2, R 3, R 4, R 7 and R 8 are the same or different, and represent a hydrogen atom or hydroxy, or R 1 and R 2, R 3 and R 4, or R 7 and R 8 together represent =O, R 5 and R 6 are the same or different, and represent a hydrogen atom, halogen, azido, hydroxy, optionally substituted lower alkoxy, optionally substituted cycloalkyloxy, optionally substituted lower alkenyloxy, optionally substituted lower alkynyloxy, optionally substituted aryloxy, optionally substituted aromatic heterocyclyloxy, optionally substituted aliphatic heterocyclyloxy, optionally substituted lower alkanoyloxy, optionally substituted aroyloxy, optionally substituted aromatic heterocyclylcarbonyloxy, or -NR b R c (wherein R b and R c are the same or different, and represent a hydrogen atom, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted cycloalkyl, optionally substituted aryl, an optionally substituted aromatic hetercyclic group, an optionally substituted aliphatic heterocyclic group, optionally substituted lower alkanoyl, optionally substituted aroyl, optionally substituted lower alkoxycarbonyl, optionally substituted aryloxycarbonyl, optionally substituted aromatic heterocyclyloxycarbonyl, optionally substituted lower alkylcarbamoyl, optionally substituted di-lower alkylcarbamoyl, optionally substituted arylcarbamoyl, optionally substituted aromatic heterocyclylcarbamoyl, optionally substituted arylsulfonyl, or optionally substituted lower alkylsulfonyl), or R 5 and R 6 together represent O=, R d ON= (wherein R d represents a hydrogen atom, optionally substituted lower alkyl, optionally substituted cycloalkyl, optionally substituted aryl, an optionally substituted aromatic hetercyclic group, or an optionally substituted aliphatic heterocyclic group), or R e R f C= (wherein R e and R f are the same or different, and represent a hydrogen atom, halogen, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted lower alkynyl, optionally substituted cycloalkyl, optionally substituted aryl, an optionally substituted aromatic heterocyclic group, an optionally substituted aliphatic heterocyclic group, optionally substituted lower alkoxy, optionally substituted aryloxy, optionally substituted aromatic heterocyclyloxy, optionally substituted lower alkanoyl, optionally substituted aroyl, optionally substituted lower alkanoyloxy, or optionally substituted aroyloxy), R 9 represents a hydrogen atom, optionally substituted lower alkyl, optionally substituted lower alkenyl, optionally substituted lower alkynyl, or optionally substituted cycloalkyl, or R 1 and R 3, R 3 and R 5 (provided that this is only when X a is a bond), R 5 and R 7 (provided that this is only when X b is a bond), or R 7 and R 9 together represent a bond or an oxgen atom, and regarding R 10, R 11 and R 12, R 10 and R 11 together represent a bond or an oxgen atom and R 12 represents a hydrogen atom, or R 10 and R 12 together represent a bond or an oxgen atom and R 11 represents a hydrogen atom] (provided that compounds represented by the following formulas and are excluded), or a pharmaceutically acceptable salt thereof; wherein in the general formula, the lower alkyl, and the lower alkyl moiety of the lower alkoxy, the lower alkanoyl, the lower alkoxycarbonyl, the lower alkanoyloxy, the lower alkylcarbamoyl, the di-lower alkylcarbamoyl and the lower alkylsulfonyl is a linear or branched alkyl having 1 to 10 carbon atoms; wherein in the general formula, the lower alkenyl, and the lower alkenyl moiety of the lower alkenyloxy is a linear or branched alkenyl having 2 to 10 carbon atoms; wherein in the general formula, the lower alkynyl, and the lower alkynyl moiety of the lower alkynyloxy is a linear or branched alkynyl having 2 to 10 carbon atoms.