A compound of the formula or a pharmaceutically acceptable salt thereof: wherein X is methylene, oxygen atom, sulfur atom, SO, SO 2 or NR 7 wherein R 7 is hydrogen atom or an alkyl group of 1 to 3 carbon atoms; R 1 and R 2 are independently hydrogen atom or a substituted or unsubstituted alkyl group of 1 to 6 carbon atoms, provided that when the alkyl group is substituted, it is substituted with 1 to 4 same or different substituents selected from the group consisting of hydroxy group, halogen atom and an alkoxy group of 1 to 6 carbon atoms; R 3 is an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or an alkylthio group of 1 to 6 carbon atoms; R 4 is hydrogen atom, halogen atom, hydroxy group, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or cyano group; Y 1 is a single bond, - (CR 9 R 10) p -, -CH=CH- (CR 9 R 10) q -, -C≡C-(CR 9 R 10) q' - or - (CR 9 R 10) r -O-(CR 9' R 10') r' - wherein R 9, R 10, R 9', and R 10' are independently hydrogen atom or an alkyl group of 1 to 4 carbon atoms; Y 2 is a single bond or -C -; L is a substituted or unsubstituted straight chain alkylene of 2 to 6 carbon atoms or a divalent group derived from 4- to 8-membered cycloalkane, provided that when the straight chain alkylene or the cycloalkane is substituted, it is substituted with 1 to 4 same or different substituents selected from the group consisting of alkyl group of 1 to 5 carbon atoms, hydroxy group and halogen atom, and any one of the methylene group in the straight chain alkylene of L is optionally replaced with carbonyl group; R 5 and R 6 are independently hydrogen atom or a substituted or unsubstituted alkyl group of 1 to 6 carbon atoms, or either R 5 or R 6 is bonded to any carbon atom of L to form a 4- to 8-membered nitrogen-containing saturated heterocycle, or R 5 and R 6 are taken together to form a substituted or unsubstituted 5- to 8-membered nitrogen-containing saturated heterocycle; provided that when the alkyl group is substituted, it is substituted with same or different 1 to 4 substituents selected from the group consisting of hydroxy group and halogen atom; when the 4- to 8-membered nitrogen-containing saturated heterocycle or the 5- to 8-membered nitrogen-containing saturated heterocycle is substituted, it is substituted with same or different 1 to 4 substituents selected from the group consisting of methyl group, ethyl group, propyl group, hydroxymethyl group, hydroxyethyl group, carbonyl group, hydroxy group and halogen atom; m is 0 or 1; p is an integer of 1 to 6; q and q' are independently an integer of 0 to 4; r is an integer of 0 to 5, and r' is an integer of 1 to 5, provided that r' is an integer of 2 or more when the sum of r and r' is 5 or less and Y 2 is a single bond; and ------ is independently a single bond or a double bond. X is methylene, oxygen atom, sulfur atom, SO, SO 2 or NR 7 wherein R 7 is hydrogen atom or an alkyl group of 1 to 3 carbon atoms; R 1 and R 2 are independently hydrogen atom or a substituted or unsubstituted alkyl group of 1 to 6 carbon atoms, provided that when the alkyl group is substituted, it is substituted with 1 to 4 same or different substituents selected from the group consisting of hydroxy group, halogen atom and an alkoxy group of 1 to 6 carbon atoms; R 3 is an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or an alkylthio group of 1 to 6 carbon atoms; R 4 is hydrogen atom, halogen atom, hydroxy group, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or cyano group; Y 1 is a single bond, - (CR 9 R 10) p -, -CH=CH- (CR 9 R 10) q -, -C≡C-(CR 9 R 10) q' - or - (CR 9 R 10) r -O-(CR 9' R 10') r' - wherein R 9, R 10, R 9', and R 10' are independently hydrogen atom or an alkyl group of 1 to 4 carbon atoms; Y 2 is a single bond or -C -; L is a substituted or unsubstituted straight chain alkylene of 2 to 6 carbon atoms or a divalent group derived from 4- to 8-membered cycloalkane, provided that when the straight chain alkylene or the cycloalkane is substituted, it is substituted with 1 to 4 same or different substituents selected from the group consisting of alkyl group of 1 to 5 carbon atoms, hydroxy group and halogen atom, and any one of the methylene group in the straight chain alkylene of L is optionally replaced with carbonyl group; R 5 and R 6 are independently hydrogen atom or a substituted or unsubstituted alkyl group of 1 to 6 carbon atoms, or either R 5 or R 6 is bonded to any carbon atom of L to form a 4- to 8-membered nitrogen-containing saturated heterocycle, or R 5 and R 6 are taken together to form a substituted or unsubstituted 5- to 8-membered nitrogen-containing saturated heterocycle; provided that when the alkyl group is substituted, it is substituted with same or different 1 to 4 substituents selected from the group consisting of hydroxy group and halogen atom; when the 4- to 8-membered nitrogen-containing saturated heterocycle or the 5- to 8-membered nitrogen-containing saturated heterocycle is substituted, it is substituted with same or different 1 to 4 substituents selected from the group consisting of methyl group, ethyl group, propyl group, hydroxymethyl group, hydroxyethyl group, carbonyl group, hydroxy group and halogen atom; m is 0 or 1; p is an integer of 1 to 6; q and q' are independently an integer of 0 to 4; r is an integer of 0 to 5, and r' is an integer of 1 to 5, provided that r' is an integer of 2 or more when the sum of r and r' is 5 or less and Y 2 is a single bond; and ------ is independently a single bond or a double bond.