Provided is a medicine to prevent or prevent recurrence of, treat or improve symptoms of gastroesophageal reflux disease for which existing treatments have no effect. 4-[({ 6-[isobutyl(1,3-thiazole-2-ylsulfonyl)amino]-2,3-dihydro-1H-indene-5-yl} oxy)methyl]-3-methyl benzoic acid, a salt thereof or a prodrug thereof is effective in preventing or preventing recurrence of, treating or improving the symptoms of gastroesophageal reflux disease.
