The present invention provides a compound of formula (I) wherein Ar represents an aromatic group which may be substituted; X represents methylene, S, SO, SO2 or CO; Y represents a spacer having a main chain of 2 to 5 atoms; n represents an integer of 1 to 5; i) R?1 and R2¿ each represents a hydrogen atom or a lower alkyl which may be substituted, ii) R?1 and R2¿ form, taken together with the adjacent nitrogen atom, a nitrogen-containing heterocyclic ring which may be substituted, or iii) R1 or R2 together with -(CH¿2?)n-N= form, bonded to a component atom of Ring B, a spiro-ring which may be substituted; Ring A represents an aromatic Ring which may be substituted; Ring B represents a 4- to 7-membered nitrogen-containing non-aromatic ring which may be further substituted by alkyl or acyl, with a proviso that X represents S, SO, SO2 or CO when Ring A has as a substituent a group represented by the formula: -NHCOR?11¿ where R11 represents alkyl, alkoxyalkyl, alkylthioalkyl, cycloalkyl, cycloalkylalkyl, aryl, arylalkyl or a group represented by the formula: -NHR12 where R12 represents alkyl, cycloalkyl, cycloalkylalkyl, aryl or arylalkyl, or a salt thereof; which has an excellent somatostatin receptor binding inhibition action.