An aqueous composition having an excellent antiseptic effect is provided. An aqueous composition containing: a compound represented by Formula (1), a salt thereof, or a solvate of the compound or the salt thereof, where X represents a halogen atom, and a quaternary ammonium surfactant. A method for producing an aqueous composition with an antiseptic effect, by incorporating a compound represented by Formula (1), a salt thereof, or a solvate of the compound or the salt thereof and a quaternary ammonium surfactant into the aqueous composition.