A method for separating an alkyl aromatic hydrocarbon, the method having a step of adding a first diluent and an extractant having a superacid to a mixture comprising the alkyl aromatic hydrocarbon and one or more isomers thereof to carry out an acid-base extraction to thereby form a complex of the alkyl aromatic hydrocarbon with the superacid, and thereafter separating the complex from the mixture, and a step of adding an eliminating agent having a relative basicity in a range of 0.06 to 10 with respect to the alkyl aromatic hydrocarbon and a second diluent to the complex, and carrying out complex exchange of the alkyl aromatic hydrocarbon for the eliminating agent to thereby separate the alkyl aromatic hydrocarbon from the complex.