To provide a thiamine disulfide derivative capable of overcoming poor solubility in water which is a defect of conventional thiamine derivatives, and having strong anti-HIV(Human Immunodeficiency Virus) activity, and to provide a medicament containing the derivative or its salt as an active ingredient, useful as a remedy for HIV infectious diseases, especially as a remedy for AIDS(Acquired Immune Deficiency Syndrome).

The thiamine disulfide derivative is represented by the general formula (1) (X1 and X2 are each H or a halogen, and may be each equal to or different from the other; and R1 is a straight-chain or branched chain alkylene) or its salt. The medicament contains the derivative or its salt as an active ingredient.