Provided are a method and an apparatus for producing 1,2,3,4-tetrachlorobutane that are unlikely to lose 3,4-dichloro-1-butene as the material or 1,2,3,4-tetrachlorobutane as the product and can be stably and economically produce 1,2,3,4-tetrachlorobutane. A reaction liquid (1) containing 3,4-dichloro-1-butene is placed in a reaction container (11), then chlorine gas is supplied to a gas phase (2) in the reaction container (11), and the 3,4-dichloro-1-butene is reacted with the chlorine gas to give 1,2,3,4-tetrachlorobutane.