Abstract: A method according to the present invention is a method for producing an ionic liquid from a molten salt solution containing a molten salt constituted by combining the cation portion and the anion portion, the ionic liquid containing the molten salt as a main component, the method comprising: removing water from the molten salt solution, the step of removing the water including adding a compound in the molten salt solution, the compound being represented by General Formula (1): where at least two of R1 to R4 are a C1 to C8 alkoxy group(s), the rest of R1 to R4 are a hydrogen atom(s) or a C1 to C8 alkyl group(s). By this, it is possible to remove water from the molten salt solution regardless of whether the molten salt solution is hydrophilic or hydrophobic. The present invention provides a method of producing an ionic liquid, which method can remove water from any kind of ionic liquid economically, easily, and quickly.