To provide a compound which has a potent agonistic activity on GHS-R and which is useful as a therapeutic agent for systemic wasting diseases such as cachexia. A 3,8-diaminotetrahydroquinoline derivative represented by formula (la) (wherein X represents CH 2 , C=O, CH-OR, CH-SR, or CH-NRR'； m is a number of 1 or 2； Ar represents a phenyl group, a naphthyl group, a 5-membered or 6-membered aromatic heterocyclic group having one or two elements selected from S, N, and O, or a similar group； R 1 and R 2 , which may be identical to or different from each other, each represent a hydrogen atom or a methyl group； R 3 represents a C1 to C6 alkyl group or a similar group； n is a number of 0 or 1； R 4 and R 5 , which may be identical to or different from each other, each represent a hydrogen atom, or a C1 to C6 alkyl group, etc.； and R 6 , R 7 , R, and R', which may be identical to or different from one another, each represent a hydrogen atom or a C1 to C6 alkyl group), or a salt thereof.
