The present invention has as its object providing substituted phenethylamine derivatives that function as a motilin receptor antagonist and which are useful as medicines. The invention provides compounds of Formula (1): <；CHEM>； wherein: Cy is a group of Formula (2): <；CHEM>； an optionally substituted heterocyclic ring, C3-7cycloalkyl or phenyl； R1, R2, R3, R4 and R5 are hydrogen, halogen, hydroxy, amino, trifluoromethyl or nitrile and at least one of R1, R2, R3, R4 and R5 is halogen, trifluoromethyl or nitrile； R6 is hydrogen, optionally substituted straight-chained or branched C1-3alkyl, amino or hydroxy； R7 is hydrogen, optionally substituted straight-chained or branched C1-3alkyl, optionally substituted amino or hydroxy； R8 is hydrogen, methyl or ethyl； R9 is optionally substituted straight-chained or branched C1-6alkyl, optionally substituted straight-chained or branched C2-6alkenyl, optionally substituted straightchained or branched C2-6alkynyl, C3-7cycloalkyl or optionally substituted phenyl； R20 is hydrogen or straight-chained or branched C1- 3alkyl or R9 and R20 may together form C3-7cycloalkyl； R10 is hydrogen or straight-chained or branched C1- 3alkyl； R11 is hydrogen, optionally substituted straight-chained or branched C1-3alkyl, -CO-N(R14)R15, carboxyl or an optionally substituted heterocyclic ring； R12 is hydroxy or -OR16； R13 is hydrogen, straight-chained or branched C1- 6alkyl, straight-chained or branched C2-6alkenyl, straight-chained or branched C2-6alkynyl or a group of Formula (3): <；CHEM>； R14 and R15, which may be the same or different, are hydrogen, optionally substituted straight-chained or branched C1-4alkyl, C3-7cycloalkyl, straight-chained or branched C1-4alkyloxy, straight-chained or branched C1-4alkylsulfonyl or a heterocyclic ring, or R14 and R15, as -N(R14)R15, form optionally substituted 3- to 7-membered cyclic amine； R16 is straight-chained C1-4alkyl； R17 is hydrogen or methyl； R18 and R19 together form
