To provide a method for treating crystallization mother liquor of alanine, by which the crystallization mother liquor of the alanine can be formed into a waste liquid capable of being suitably subjected to a burning treatment without damaging a furnace wall of an incinerator and without generating soot and smoke including air pollutants such as sulfur dioxide and nitrogen oxides.

This method for treating crystallization mother liquor of alanine comprises separating impurities such as an alkali component and others from the crystallization mother liquor of the aniline by an electrodialysis. Preferably, the electrodialysis is carried out by introducing the crystallization mother liquor to a room (b), which is one of the rooms between an anion exchange membrane A and a cation exchange membrane C in an apparatus constituted of basic units comprising a bipolar membrane B, the anion exchange membrane A, the cation exchange membrane C and the bipolar membrane B arranged in order, collecting byproducts from the room (a) between the bipolar membrane B and the anion exchange membrane A as a waste material, and collecting an alkaline component (sodium hydroxide) from a room (c) between the cation exchange membrane C and the bipolar membrane B.