A compound represented by the formula or a pharmaceutically acceptable salt thereof: wherein Ar 11 is a C 6-10 aryl group having substituent (s), a C 1-9 heteroaryl group having substituent(s), or a C 3-7 cycloalkyl group having substituent(s); Ar 21 is a C 6-10 aryl group having substituent (s), a C 1-9 heteroaryl group having substituent(s), or a C 3-7 cycloalkyl group having substituent(s); partial structure is a divalent group of a 5-membered heteroaromatic ring (ring A 1) containing any 1 to 4 hetero atoms selected from a nitrogen atom, a sulfur atom and an oxygen atom, and optionally having 1 - 3 substituents; W 1 is C (R b1) (R c1) or a single bond; X 1 is C(R d1) (P e1), a sulfur atom, or a single bond; Y 1 is C (R f1) (R g1) or a single bond; when any two of W 1, X 1 and Y 1 are single bonds, the remaining one is not a single bond; R b1 - R g1 are the same or different and each is a hydrogen atom, a C 1-6 alkyl group, a C 2-6 alkenyl group, a C 2-6 alkynyl group, a halogeno-C 1-6 alkyl group, a C 1-6 alkoxy group, a hydroxyl group, a halogeno-C 1-6 alkoxy group, an amino group, an amino group mono- or di-substituted by a C 1-6 alkyl group, or a halogeno group; respective R b1 - R g1 on the adjacent carbon atoms are optionally joined to form a double bond and/or a ring; R 11 is a hydrogen atom, a hydroxyl group, a C 2-6 alkenyl group, a C 2-6 alkynyl group, a halogeno-C 1-6 alkyl group, a cyclic C 3-6 alkyl group, or a C 1-6 alkyl group substituted by a cyclic C 3-6 alkyl group; R 21 and R 31 are the same or different and each is a hydrogen atom, a halogen atom, a hydroxyl group, a C 1-6 alkyl group, a C 2-6 alkenyl group, a C 2-6 alkynyl group, a cyclic C 3-6 alkyl group (optionally containing a hetero atom in the ring), a C 6-10 aryl group optionally having substituent(s), a C 1-9 heteroaryl group optionally having substituent(s), a C 1-6 alkyl group substituted by a hydroxyl group, a C 1-6 alkyl group substituted by a C 6-10 aryl group optionally having substituent (s), or a C 1-6 alkyl group substituted by a C 1-9 heteroaryl group optionally having substituent(s), and R 41 is a hydrogen atom, a C 1-6 alkyl group, a C 2-6 alkenyl group, or a C 2-6 alkynyl group; when R 21 or R 31 is a methyl group, Ar 21 is not a phenyl group substituted by a fluorine atom; when Ar 11 is a phenyl group substituted by a fluorine atom, ring A 1 in partial structure is not furan or thiophene; when Ar 11 is a phenyl group substituted by a methoxy group, ring A 1 in partial structure is not thiophene; and when Ar 11 is a phenyl group substituted by a methyl group, ring A 1 in partial structure is not oxadiazole, and Ar 21 is not a methoxyphenyl group. Ar 11 is a C 6-10 aryl group having substituent (s), a C 1-9 heteroaryl group having substituent(s), or a C 3-7 cycloalkyl group having substituent(s); Ar 21 is a C 6-10 aryl group having substituent (s), a C 1-9 heteroaryl group having substituent(s), or a C 3-7 cycloalkyl group having substituent(s); partial structure is a divalent group of a 5-membered heteroaromatic ring (ring A 1) containing any 1 to 4 hetero atoms selected from a nitrogen atom, a sulfur atom and an oxygen atom, and optionally having 1 - 3 substituents; W 1 is C (R b1) (R c1) or a single bond; X 1 is C(R d1) (P e1), a sulfur atom, or a single bond; Y 1 is C (R f1) (R g1) or a single bond; when any two of W 1, X 1 and Y 1 are single bonds, the remaining one is not a single bond; R b1 - R g1 are the same or different and each is a hydrogen atom, a C 1-6 alkyl group, a C 2-6 alkenyl group, a C 2-6 alkynyl group, a halogeno-C 1-6 alkyl group, a C 1-6 alkoxy group, a hydroxyl group, a halogeno-C 1-6 alkoxy group, an amino group, an amino group mono- or di-substituted by a C 1-6 alkyl group, or a halogeno group; respective R b1 - R g1 on the adjacent carbon atoms are optionally joined to form a double bond and/or a ring; R 11 is a hydrogen atom, a hydroxyl group, a C 2-6 alkenyl group, a C 2-6 alkynyl group, a halogeno-C 1-6 alkyl group, a cyclic C 3-6 alkyl group, or a C 1-6 alkyl group substituted by a cyclic C 3-6 alkyl group; R 21 and R 31 are the same or different and each is a hydrogen atom, a halogen atom, a hydroxyl group, a C 1-6 alkyl group, a C 2-6 alkenyl group, a C 2-6 alkynyl group, a cyclic C 3-6 alkyl group (optionally containing a hetero atom in the ring), a C 6-10 aryl group optionally having substituent(s), a C 1-9 heteroaryl group optionally having substituent(s), a C 1-6 alkyl group substituted by a hydroxyl group, a C 1-6 alkyl group substituted by a C 6-10 aryl group optionally having substituent (s), or a C 1-6 alkyl group substituted by a C 1-9 heteroaryl group optionally having substituent(s), and R 41 is a hydrogen atom, a C 1-6 alkyl group, a C 2-6 alkenyl group, or a C 2-6 alkynyl group; when R 21 or R 31 is a methyl group, Ar 21 is not a phenyl group substituted by a fluorine atom; when Ar 11 is a phenyl group substituted by a fluorine atom, ring A 1 in partial structure is not furan or thiophene; when Ar 11 is a phenyl group substituted by a methoxy group, ring A 1 in partial structure is not thiophene; and when Ar 11 is a phenyl group substituted by a methyl group, ring A 1 in partial structure is not oxadiazole, and Ar 21 is not a methoxyphenyl group.