The present invention provides: 4-methyl-2-[4-(2-methylpropoxy)-3-(1H-1,2,3,4-tetrazole-1-yl)phenyl]-1,3thiazole-5-carboxylic acid and a sodium salt thereof that are useful as a therapeutic agent or a prophylactic agent for gout, hyperuricemia, and the like; crystals thereof; and a production method therefor.