A process for producing crystals of 2-ethoxy-1-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-1H-benzimidazole-- 7-carboxylic acid (compound (I)), characterized by dissolving or suspending the compound (I) or a salt thereof in a solvent comprising an aprotic polar solvent and crystallizing it. By the process, the contaminants which are contained in the compound (I) or its salt and are difficult to remove, such as tin compounds, analogues of the compound (I), and a residual organic solvent, can be easily removed. Crystals of the compound (I) can be efficiently and easily mass-produced in high yield on an industrial scale.