A compound represented by the formula: wherein Q is =O or =S; ring A is a 6-membered monocyclic aromatic ring or heteroaromatic ring, or a bicyclic aromatic ring or heteroaromatic ring; A 1 is -C(Ra)= or -N=; A 2 is -C(Rb)= or -N=; A 3 is -C(Rc)= or -N=; A 4 is -C(Rd)= or -N=; Ra, Rb, Rc and Rd are the same or different and each is hydrogen, a halogeno group, a cyano group, a hydroxy group, a C 1-6 alkyl group, a C 1-6 alkoxy group, a halogenoC 1-6 alkyl group or a halogenoC 1-6 alkoxy group; provided at least two of A 1 - A 4 are not -N=; R 1 is hydrogen or a C 1-6 alkyl group optionally having substituent(s); R 2 is hydrogen, a C 1-6 alkyl group optionally having substituent(s) or a C 2-6 alkenyl group optionally having substituent(s); R 3 is hydrogen or a C 1-6 alkyl group; R 4 is hydrogen or a C 1-6 alkyl group; R 5 is hydrogen or a C 1-6 alkyl group; R 1 and R 2 are optionally joined to form a nitrogen-containing ring optionally having substituent(s); R 4 and R 5 are optionally joined to form cycloalkane; X is hydrogen, -Cy, -C(R x1 R x2)-Cy, -C(R x1 R x2) -C(R x3 R x4)-Cy, -C(R x1)=C(R x2)-Cy, -O-Cy, -O-C(R x1 R x2)-Cy, -C(R x1 R x2)-O-Cy, -S n-Cy, -S n-C(R x1 R x2) -Cy, -C(R x1 R x2)-S n-Cy, -N(R x5)-Cy, -N(R x5)-C(R x1 R x2)-Cy, -C(R x1 R x2)-N(R x5)-Cy, -N(R x5)-N(R x6)-Cy, -O-N(R x5)-Cy, -N(R x5)-O-Cy, -C -N(R x5)-Cy, -N(R x5)-C -Cy, -S m-N(R x5)-Cy, -N(R x5)-S m-Cy, -O-S m-Cy, or -S m-O-Cy; n is an integer of 0 - 2; m is 1 or 2; Cy is a saturated or unsaturated cyclic group optionally having substituent(s) (optionally containing a hetero atom); R x1, R x2, R x3, R x4, R x5 and R x6 are the same or different and each is hydrogen, a C 1-6 alkyl group optionally having substituent(s) or a C 1-6 alkoxycarbonyl group optionally having substituent(s); R 6 is a C 1-6 alkyl group optionally having substituent (s), a C 2-6 alkenyl group, a cyclic C 3-6 alkyl group (optionally containing a hetero atom), a halogeno group, a hydroxy group, a C 1-6 alkoxy group optionally having substituent(s), a halogenoC 1-6 alkyl group, a halogenoC 1-6 alkoxy group, an amino group, an amino group mono- or di-substituted by a C 1-6 alkyl group optionally having substituent(s), a cyano group, a C 1-6 alkylthio group, a carboxyl group, a C 1-6 alkoxycarbonyl group optionally having substituent(s), a carbamoyl group, a carbamoyl group mono- or di-substituted by a C 1-6 alkyl group optionally having substituent(s), or an amino group substituted by an acyl group optionally having substituent(s); when R 6 is present in plurality, they may be the same or different; and k is an integer of 0 - 3, or a pharmaceutically acceptable salt thereof, excluding the following compound: Q is =O or =S; ring A is a 6-membered monocyclic aromatic ring or heteroaromatic ring, or a bicyclic aromatic ring or heteroaromatic ring; A 1 is -C(Ra)= or -N=; A 2 is -C(Rb)= or -N=; A 3 is -C(Rc)= or -N=; A 4 is -C(Rd)= or -N=; Ra, Rb, Rc and Rd are the same or different and each is hydrogen, a halogeno group, a cyano group, a hydroxy group, a C 1-6 alkyl group, a C 1-6 alkoxy group, a halogenoC 1-6 alkyl group or a halogenoC 1-6 alkoxy group; provided at least two of A 1 - A 4 are not -N=; R 1 is hydrogen or a C 1-6 alkyl group optionally having substituent(s); R 2 is hydrogen, a C 1-6 alkyl group optionally having substituent(s) or a C 2-6 alkenyl group optionally having substituent(s); R 3 is hydrogen or a C 1-6 alkyl group; R 4 is hydrogen or a C 1-6 alkyl group; R 5 is hydrogen or a C 1-6 alkyl group; R 1 and R 2 are optionally joined to form a nitrogen-containing ring optionally having substituent(s); R 4 and R 5 are optionally joined to form cycloalkane; X is hydrogen, -Cy, -C(R x1 R x2)-Cy, -C(R x1 R x2) -C(R x3 R x4)-Cy, -C(R x1)=C(R x2)-Cy, -O-Cy, -O-C(R x1 R x2)-Cy, -C(R x1 R x2)-O-Cy, -S n-Cy, -S n-C(R x1 R x2) -Cy, -C(R x1 R x2)-S n-Cy, -N(R x5)-Cy, -N(R x5)-C(R x1 R x2)-Cy, -C(R x1 R x2)-N(R x5)-Cy, -N(R x5)-N(R x6)-Cy, -O-N(R x5)-Cy, -N(R x5)-O-Cy, -C -N(R x5)-Cy, -N(R x5)-C -Cy, -S m-N(R x5)-Cy, -N(R x5)-S m-Cy, -O-S m-Cy, or -S m-O-Cy; n is an integer of 0 - 2; m is 1 or 2; Cy is a saturated or unsaturated cyclic group optionally having substituent(s) (optionally containing a hetero atom); R x1, R x2, R x3, R x4, R x5 and R x6 are the same or different and each is hydrogen, a C 1-6 alkyl group optionally having substituent(s) or a C 1-6 alkoxycarbonyl group optionally having substituent(s); R 6 is a C 1-6 alkyl group optionally having substituent (s), a C 2-6 alkenyl group, a cyclic C 3-6 alkyl group (optionally containing a hetero atom), a halogeno group, a hydroxy group, a C 1-6 alkoxy group optionally having substituent(s), a halogenoC 1-6 alkyl group, a halogenoC 1-6 alkoxy group, an amino group, an amino group mono- or di-substituted by a C 1-6 alkyl group optionally having substituent(s), a cyano group, a C 1-6 alkylthio group, a carboxyl group, a C 1-6 alkoxycarbonyl group optionally having substituent(s), a carbamoyl group, a carbamoyl group mono- or di-substituted by a C 1-6 alkyl group optionally having substituent(s), or an amino group substituted by an acyl group optionally having substituent(s); when R 6 is present in plurality, they may be the same or different; and k is an integer of 0 - 3, or a pharmaceutically acceptable salt thereof, excluding the following compound: