There has been no report of the existence of crystalline polymorphism in reduced coenzyme Q10, and it has been considered that a conventionally obtained crystal form is the only one crystal form of reduced coenzyme Q10. The invention relates to a reduced coenzyme Q10 crystal having an endothermic peak showing melting at 54 ± 2ºC when the temperature is raised at a rate of 5ºC/min in differential scanning calorimetry (DSC) and/or a reduced coenzyme Q10 crystal showing characteristic peaks at diffraction angles (2? ± 0.2º) of 11.5º, 18.2º, 19.3º, 22.3º, 23.0º, and 33.3º in powder X-ray (Cu-Ka) diffraction. The crystal form is a novel reduced coenzyme Q10 crystal which has a higher melting point than the conventionally known reduced coenzyme Q10 crystal, has low solubility in a solvent, and therefore has excellent stability.
