Excellent stability reduced coenzyme q10 crystal

For the reduced coenzyme Q10, no reports of the crystal polymorphism is present, it has been considered that the crystalline forms are obtained conventionally is the only one. The present invention, by differential scanning calorimetry (DSC), when the temperature was raised at a 5 ° C. / minute rate, the reduced coenzyme Q10 having an endothermic peak showing the melting 54? 2 ° C. crystals, and / or, in the powder X-ray (Cu-Kα) diffraction, the diffraction angle (2θ? 0.2?) 11.5?, 18.2?, 19.3?, 22.3?, 23.0? and 33.3? to about reduced coenzyme Q10 crystal showing characteristic peaks. The crystalline form known reduced coenzyme Q10 higher melting point than the crystal, a low solubility in solvents, is excellent in stability novel crystals of reduced coenzyme Q10.