The present invention provides a novel form of 3-(3-{4-[3-(β-D-glucopyranosyloxy)-5-isopropyl-1H-pyrazol-4-ylmethyl]-3-methylphenoxy}propylamino)-2,2-dimethylpropionamide with improved storage stability. Since bis[3-(3-{4-[3-(β-D-glucopyranosyloxy)-5-isopropyl-1H-pyrazol-4-ylmethyl]-3-methylphenoxy}propylamino)-2,2-dimethylpropionamide]monosebacate has extremely excellent storage stability, it is useful as a drug substance. Furthermore, it shows an extremely good crystalline property and can be purified by a convenient method, and therefore is suitable for the industrial preparation.