A method for purifying a treatment target solution which can remove a compound having an aliphatic hydrocarbon group which has at least one ionic group and a fluorine atom efficiently is provided.
The method for purifying a treatment target solution of the present invention comprises bringing a treatment target solution containing a compound having an aliphatic hydrocarbon group which has at least one ionic group selected from the group consisting of a carboxylic acid group and a sulfonic acid group, and a fluorine atom and may contain an oxygen atom, at least one acid selected from the group consisting of HF and H2SO4 and water, into contact with a resin having a tertiary amino group to remove the compound having an aliphatic hydrocarbon group from the treatment target solution.