There are provided: 4-methyl-2-[4-(2-methylpropoxy)-3-(1H-1,2,3,4-tetrazol-1-yl)phenyl]-1,3-thiazole-5-carboxylic acid, a sodium salt thereof and crystals of these, useful as a therapeutic agent and a prophylactic agent for gout, hyperuricemia and the like, and a method for producing the same.