The present invention relates to an epidithiodioxopiperazine derivative represented by the following Chemical Formula 1 or its reduced derivative; a method for preparing a compound represented by Chemical Formula 1 having improved intracellular permeability and mimicking the activity of 2-Cys-Prx in its reduced form in the cells; a pharmaceutical composition for preventing or treating vascular diseases comprising an epidithiodioxopiperazine compound or its derivatives or pharmaceutically acceptable salts thereof as an active ingredient; a drug delivery device for local administration including the pharmaceutical composition; and a pharmaceutical composition for inhibiting melanoma metastasis comprising the epidithiodioxopiperazine compound or its derivatives or pharmaceutically acceptable salts thereof as an active ingredient.