Provided is a composition for removing a sulfur-containing compound present in liquid or vapor, the sulfur-containing compound being hydrogen sulfide, an —SH group-containing compound or a mixture thereof, the composition containing an α,β-unsaturated aldehyde represented by the following general formula (1) as an active ingredient; wherein R1 and R2 each independently represent an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms, or are connected to each other to represent an alkylene group having 2 to 6 carbon atoms; and R3 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, or is connected to R1 to represent an alkylene group having 2 to 6 carbon atoms.