The present invention relates to an arylalkylamine compound represented by the following formula [I] or a pharmaceutically acceptable salt thereof, a process for preparing the same, and use of the above-mentioned compound as an activating compound (CaSR agonist) of a Ca sensiing receptor, a pharmaceutical composition containing the above-mentioned compound as an effective ingredient, etc. The symbols in the formula represent the following meanings: Ar: optionally substituted aryl or optionally substituted heteroaryl here, the cyclic portion of the heteroaryl is bicyclic heterocyclic ring in which 5- to 6-membered monocyclic heterocyclic ring containing 1 or 2 hetero atom(s) and benzene ring are fused； R 1 : a group selected from the group consisting of optionally substituted cyclic hydrocarbon group, and optionally substituted heterocyclic group； n: an integer of 1 to 3； X: single bonding arm, -CH 2 -, -CO- , - (CH 2 ) m -CO- , -CH (R 2 ) -CO-, - (CH 2 ) p -Y-(C(R 3 ) (R 4 )) q -CO-, -NH-CO- or -N(R 5 ) -CO-； in the above-mentioned respective definitions of the X, the bonding arm described at the left end represents a bond with R 1 ； m is an integer of 1 to 3； p is an integer of 0 to 2； q is an integer of 0 to 2； Y: -O- or -SO 2 -； R 2 : phenyl or lower alkyl； R 3 , R 4 : each independently represents hydrogen atom or lower alkyl； R 5 : lower alkyl； provided that the ring portion of the group represented by R 1 is neither naphthylidine nor partially saturated group thereof, and, when X is -CH 2 - or -CO-, R 1 is not naphthyl.
