MS-based screening method was developed for stevia sweetener in processed foods. After extraction of stevia sweetener from processed foods by dialysis, the dialysate was diluted with water, and stevia sweetener was measured by LC-MS/MS. Recovery from 5 kinds of processed foods spiked with 10 mg/kg of stevioside SS , 10 mg/kg of rebaudioside A RS , or 100 mg/kg of α -glucosyltransferase-treated stevia Gts product was excellent, and no interfering peak was observed. Thirty-six commercial processed foods indicated as containing stevia were analyzed using this established method. Among them, 33 contained SS, 33 contained RS, and 11 contained Gts. Five products contained both stevia extract and Gts.