A compound of formula I, or a pharmaceutically acceptable salt thereof: wherein, X is oxygen or sulfur; Y is C 1-7 alkyl, C 2-7 alkenyl, C 2-7 alkynyl, C 1-7 alkoxy, C 1-7 alkoxy-C 1-7 alkyl, C 1-7 alkylsulfinyl, C 1-7 alkylsulfonyl, or C 1-7 alkylthio; ring A is selected from the group consisting of: said W being, halogen, said R 2 being each independently hydroxy, C 1-7 alkyl, or C 1-7 alkoxy, and said n being an integer of 0 to 3; ring B is wherein, said R 5a, R 5b, R 6a, and R 6b being each independently selected from the group consisting of hydrogen, halogen, hydroxy, mercapto, cyano, nitro, amino, carboxy, oxo, C 1-7 alkyl, C 1-7 alkylthio, C 2-7 alkenyl, C 2-7 alkynyl, C 1-7 alkoxy, C 1-7 alkoxy-C 1-7 alkyl, C 2-7 alkenyl-C 1-7 alkyloxy, C 2-7 alkynyl-C 1-7 alkyloxy, C 3-10 cycloalkyl, C 3-7 cycloalkylthio, C 5-10 cycloalkenyl, C 3-10 cycloalkyloxy, C 3-10 cycloalkyloxy-C 1-7 alkoxy, phenyl-C 1-7 alkyl, C 1-7 alkylthio-phenyl, phenyl-C 1-7 alkoxy, mono- or di-C 1-7 alkylamino, mono- or di-C 1-7 alkylamino-C 1-7 alkyl, C 1-7 alkanoyl, C 1-7 alkanoylamino, C 1-7 alkylcarbonyl, C 1-7 alkoxycarbonyl, carbamoyl, mono- or di-C 1-7 alkylcarbamoyl, C 1-7 alkylsulfonylamino, phenylsulfonylamino, C 1-7 alkylsulfinyl, C 6-14 arylsulfanyl, C 6-14 arylsulfonyl, C 6-14 aryl, 5 to 13-membered heteroaryl, 5 to 10-membered heterocycloalkyl, 5 to 10-membered heterocycloalkyl-C 1-7 alkyl, or 5 to 10-membered heterocycloalkyl-C 1-7 alkoxy, and said ring C being C 3-10 cycloalkyl, C 5-10 cycloalkenyl, C 6-14 aryl, 5 to 13-membered heteroaryl, or 5 to 10-membered heterocycloalkyl; said alkyl, alkenyl, alkynyl, or alkoxy is optionally substituted with at least one substituent selected from the group consisting of halogen, hydroxy, cyano, nitro, amino, mercapto, C 1-7 alkyl, and C 2-7 alkynyl; and said cycloalkyl, cycloalkenyl, aryl, heteroaryl, or heterocycloalkyl is optionally substituted with at least one substituent selected from the group consisting of halogen, hydroxy, cyano, nitro, amino, mercapto, C 1-4 alkyl, and C 1-4 alkoxy. X is oxygen or sulfur; Y is C 1-7 alkyl, C 2-7 alkenyl, C 2-7 alkynyl, C 1-7 alkoxy, C 1-7 alkoxy-C 1-7 alkyl, C 1-7 alkylsulfinyl, C 1-7 alkylsulfonyl, or C 1-7 alkylthio; ring A is selected from the group consisting of: said W being, halogen, said R 2 being each independently hydroxy, C 1-7 alkyl, or C 1-7 alkoxy, and said n being an integer of 0 to 3; said W being, halogen, said R 2 being each independently hydroxy, C 1-7 alkyl, or C 1-7 alkoxy, and said n being an integer of 0 to 3; ring B is wherein, said R 5a, R 5b, R 6a, and R 6b being each independently selected from the group consisting of hydrogen, halogen, hydroxy, mercapto, cyano, nitro, amino, carboxy, oxo, C 1-7 alkyl, C 1-7 alkylthio, C 2-7 alkenyl, C 2-7 alkynyl, C 1-7 alkoxy, C 1-7 alkoxy-C 1-7 alkyl, C 2-7 alkenyl-C 1-7 alkyloxy, C 2-7 alkynyl-C 1-7 alkyloxy, C 3-10 cycloalkyl, C 3-7 cycloalkylthio, C 5-10 cycloalkenyl, C 3-10 cycloalkyloxy, C 3-10 cycloalkyloxy-C 1-7 alkoxy, phenyl-C 1-7 alkyl, C 1-7 alkylthio-phenyl, phenyl-C 1-7 alkoxy, mono- or di-C 1-7 alkylamino, mono- or di-C 1-7 alkylamino-C 1-7 alkyl, C 1-7 alkanoyl, C 1-7 alkanoylamino, C 1-7 alkylcarbonyl, C 1-7 alkoxycarbonyl, carbamoyl, mono- or di-C 1-7 alkylcarbamoyl, C 1-7 alkylsulfonylamino, phenylsulfonylamino, C 1-7 alkylsulfinyl, C 6-14 arylsulfanyl, C 6-14 arylsulfonyl, C 6-14 aryl, 5 to 13-membered heteroaryl, 5 to 10-membered heterocycloalkyl, 5 to 10-membered heterocycloalkyl-C 1-7 alkyl, or 5 to 10-membered heterocycloalkyl-C 1-7 alkoxy, and said ring C being C 3-10 cycloalkyl, C 5-10 cycloalkenyl, C 6-14 aryl, 5 to 13-membered heteroaryl, or 5 to 10-membered heterocycloalkyl; said R 5a, R 5b, R 6a, and R 6b being each independently selected from the group consisting of hydrogen, halogen, hydroxy, mercapto, cyano, nitro, amino, carboxy, oxo, C 1-7 alkyl, C 1-7 alkylthio, C 2-7 alkenyl, C 2-7 alkynyl, C 1-7 alkoxy, C 1-7 alkoxy-C 1-7 alkyl, C 2-7 alkenyl-C 1-7 alkyloxy, C 2-7 alkynyl-C 1-7 alkyloxy, C 3-10 cycloalkyl, C 3-7 cycloalkylthio, C 5-10 cycloalkenyl, C 3-10 cycloalkyloxy, C 3-10 cycloalkyloxy-C 1-7 alkoxy, phenyl-C 1-7 alkyl, C 1-7 alkylthio-phenyl, phenyl-C 1-7 alkoxy, mono- or di-C 1-7 alkylamino, mono- or di-C 1-7 alkylamino-C 1-7 alkyl, C 1-7 alkanoyl, C 1-7 alkanoylamino, C 1-7 alkylcarbonyl, C 1-7 alkoxycarbonyl, carbamoyl, mono- or di-C 1-7 alkylcarbamoyl, C 1-7 alkylsulfonylamino, phenylsulfonylamino, C 1-7 alkylsulfinyl, C 6-14 arylsulfanyl, C 6-14 arylsulfonyl, C 6-14 aryl, 5 to 13-membered heteroaryl, 5 to 10-membered heterocycloalkyl, 5 to 10-membered heterocycloalkyl-C 1-7 alkyl, or 5 to 10-membered heterocycloalkyl-C 1-7 alkoxy, and said ring C being C 3-10 cycloalkyl, C 5-10 cycloalkenyl, C 6-14 aryl, 5 to 13-membered heteroaryl, or 5 to 10-membered heterocycloalkyl; said alkyl, alkenyl, alkynyl, or alkoxy is optionally substituted with at least one substituent selected from the group consisting of halogen, hydroxy, cyano, nitro, amino, mercapto, C 1-7 alkyl, and C 2-7 alkynyl; and said cycloalkyl, cycloalkenyl, aryl, heteroaryl, or heterocycloalkyl is optionally substituted with at least one substituent selected from the group consisting of halogen, hydroxy, cyano, nitro, amino, mercapto, C 1-4 alkyl, and C 1-4 alkoxy.