The present invention aims at provision of a quinoline derivative having a neurokinin 2 (NK2) receptor antagonistic action and relates to a compound represented by the formula (I) wherein R1 is a hydrogen atom and the like; R2 is a hydrogen atom, a hydrocarbon group optionally having substituent(s) and the like; R3 is unsubstituted (i.e., absence), a hydrogen atom and the like; R4 and R5 are the same or different and each is a hydrogen atom, a hydrocarbon group optionally having substituent(s), and the like; R6 is (cyclic group optionally having substituent(s))-carbonyl, and the like; R7, R8, R9 and R10 are the same or different and each is a hydrogen atom, halogen and the like; or R7 and R8, R8 and R9, and R9 and R10 may form a ring together with the adjacent carbon atoms; n is an integer of 1 to 5; --- represents unsubstituted (i.e., absence) or a single bond; and represents a single bond or a double bond, or a salt thereof, and the like.