Ethylamine derivatives that function as a motilin receptor antagonist and are useful as medicines are represented by the general formula (1): wherein R1 represents a phenyl group or the like, R2 represents a hydrogen atom and the like, R3 represents a hydrogen atom and the like, R4 represents a hydrogen atom and the like, R5 represents an alkyl group and the like, R7 represents a hydrogen atom and the like and R8 represents a heterocyclic ring and the like; or a hydrate or pharmaceutically acceptable salt thereof.