Process for refining methacylic acid

A process for producing refined methacrylic acid comprises the steps of oxidizing a pre-cursor such as methacrolein catalytically in a vapor phase to form a methacrylic acid-containing gas, cooling and condensing the gas to make an aqueous methacrylic acid solution, adding to the solution an immiscible organic solvent to carry out an extraction operation and thereby to obtain an organic extract containing methacrylic acid, bringing the extract into contact with water and mixing them together, separating the mixture into an organic phase and a water phase, and distilling the organic phase. Highly refined methacrylic acid containing minimal amounts of dibasic acids such as maleic acid and citraconic acid can be obtained economically and without increasing wastes that are unrecoverable to the process.