Psoriasis is a chronic, recurrent skin disease without any cure so far. The symptoms of the guttate psoriasis of Soyangins going through tonsillitis and of the psoriasis under the steroid rebound phenomenon are identical to one of yang poison exanthema of a Soyangin. The study administered Yangdokbagho-tang, which is used to cure yang poison exanthema of Soyangins, and, as a result, showed significant treatment results from these two types of four clinical cases. Sasang medicine is considered an effective treatment method to cure psoriasis, an obstinate skin disease.