To prepare anion exchange membranes which permeate specific anions selectively in electrodialysis, anion exchange membranes with various anion exchange groups were prepared and the relative transport number of various anions compared with chloride ions was examined. Anion exchange groups introduced in the membranes were trimethylbenzylammonium, triethylbenzylammonium, tri-n-propylbenzylammonium, tri-n-butylbenzylammonium, and tri-n-pentylbenzylammonium, in order of increasing hydrophobicity. The relative transport number of various anions compared with chloride ions changed remarkably with increasing chain length of alkyl groups (increasing hydrophobicity of the groups). The relative transport number of highly hydrated anions, such as sulfate ions and fluoride ions, compared with chloride ions decreased with increasing hydrophobicity of the groups. On the other hand, less hydrated anions such as bromide ions and nitrate ions compared with chloride ions permeate selectively through the membrane with increasing hydrophobicity of the groups. For example, the relative transport number of nitrate ions compared with chloride ions increased from 1.58 (membrane with trimethylbenzylammonium groups) to 16.5 (membrane with tri-n-pentylbenzylammonium groups) in electrodialysis of a 1:1 mixed solution of sodium nitrate and sodium chloride (0.04 N as sodium ion concentration). However, the increase in hydrophilicity of the membrane by further reaction of the remaining chloromethyl groups of the membrane with trimethylamine caused the relative transport number between them to decrease.