The industrial production of 4-(2-methyl-1-imidazolyl)-2,2-diphenylbutanamide, a urinary incontinence remedy, necessitates elimination of problems concerning the use of a synthetic adsorbent, e.g., HP-20, the efficiency of operation with the same, purification efficiency, etc. An acid salt, e.g., hydrochloride or phosphate, of 4-(2-methyl-1-imidazolyl)-2,2-diphenylbutanamide or a hydrate of any of these salts is used as an intermediate. This intermediate is neutralized and then purified. Thus, high-purity 4-(2-methyl-1-imidazolyl)-2,2-diphenylbutanamide is easily obtained in satisfactory yield. The industrial-scale production process has been thus established.