An oxazolidone derivative represented by formula (I) which has a monoamine oxidase inhibition effect: ##STR1## {wherein A and B each represents a nitrogen atom, a sulfur atom or an oxygen atom, with the proviso than at least one of A and B must be a nitrogen atom,R.sup.1 represents a group of the formula: ##STR2## (in which n and m each represents 0 or an integer of 1 to 4, and R.sup.3 and R.sup.4 each represents a hydrogen atom, a hydroxyl group, a lower alkyl group, etc. ), a group represented by the formula: ##STR3## (in which p and q each represents 0 or an integer of 1 to 4 and X represents an oxygen atom, sulfur atom, etc.) and a group represented by the formula: ##STR4## R.sup.2 represents a hydrogen atom or a lower alkyl group}.