Abstract: The present invention relates to a pharmaceutical composition for treating STK11-mutation cancer, containing, as an active ingredient, a material inhibiting a sodium-potassium transport function of Na+—K+ ATPase (ATP1A1); an anticancer drug containing the composition as an active ingredient; and a method for screening STK11-mutation cancer therapeutic agent. It was first established that, of cancer cells in which various gene mutations are confirmed, an STK11-mutation cancer cell line, which is confirmed at high frequency, was treated with cardiac glycosides as a material inhibiting a sodium-potassium transport function of Na+—K+ ATPase (ATP1A1), to significantly inhibit the growth of cancer cells. Therefore, the material inhibiting a sodium-potassium transport function of Na+—K+ ATPase (ATP1A1) can be a target for treating SK11-mutation-derived cancer.