To provide an ionic liquid which has a constant quality, and can be used, for example, as a solvent for enzymatic reactions, and to provide a method for producing the same.

This ionic liquid having a halide ion concentration of ≤70 ppm is obtained by (1) removing the halide ion impurity in the ionic liquid with activated alumina, (2) further removing the halide ion impurity in the ionic liquid with neutral activated alumina among the activated alumina, and (3) effectively removing the halide ion impurity in the ionic liquid with column chromatography using a column filled with neutral activated alumina.