Abstract: Provided are compounds which are an NMDA antagonist having a broad safety margin and are useful as a treating agent or a preventing agent for Alzheimer's disease, cerebrovascular dementia, Parkinson's disease, ischemic apoplexy, pain, etc. Concretely provided are an amine derivative or its salt characterized in that the amine-containing structure A therein bonds to a 2- or 3-cyclic condensed ring (e.g., indane, tetralone, 4,5,6,7-tetrahydrobenzothiophene, 4,5,6,7-tetrahydrobenzofuran, 7,8-dihydro-6H-indeno[4,5-b]furan, 2,3-dihydro-1H-cyclopenta[1]naphthalene) via X1 (bond or lower alkylene); and an NMDA antagonist containing it as an active ingredient thereof.