The present invention relates to a crystal of glutathione trisulfide dihydrate and a method for producing the same. According to the present invention, for example, the crystal can be provided by concentrating an aqueous solution in which glutathione trisulfide is dissolved and collecting the precipitated crystal of glutathione trisulfide dihydrate. In addition, the present invention relates to a simple method for producing polysulfide in an aqueous solvent using thiosulfate without using hydrogen sulfide, by stirring an aqueous solution in which a compound having a thiol group or a disulfide bond and thiosulfate are dissolved or by leaving the aqueous solution to stand.
