This study reported a clinical effect of Gamisoyo-san focussing on improvement of postoperative pain in thyroid cancer patients. Three thyroid cancer patients hospitalized at Wonkwang hospital were enrolled this study. These patients complained postoperative pain after thyroidectomy due to thyroid cancer. All patients was prescribed Gamisoyo-san. Subjective degree of pain in each patient was investigated daily. Postoperative pain of all patients were gradually relieved after treatment. In one of three case, postoperative pain relieved completely. These results suggest potential of Gamisoyo-san as effective medicine of postoperative pain after thyroidectomy in thyroid cancer patients.