The present invention provides a compound of formula (I) or a salt thereof, wherein R1, R2 and R3 are independently selected from the group consisting of hydrogen atom, fluorine atom, chlorine atom, bromine atom, C1-6 alkyl, C1-6 alkoxy substituted with fluorine atom, and others R4 and R5 are independently selected from the group consisting of hydrogen atom, fluorine atom, chlorine atom, C1-6 alkyl, C1-6 alkoxy substituted with fluorine atom, and others R6 and R7 are independently selected from the group consisting of hydrogen atom, fluorine atom, methyl, ethyl, hydroxy group, and others and R8 and R9 are independently selected from the group consisting of hydrogen atom, C1-6 alkyl, and others, which is useful as an agent for treating or preventing various types of epilepsy including partial seizures and/or generalized seizures.
