A method for predicting a therapeutic effect of chemotherapy with a combination drug containing tegafur, gimeracil, and oteracil potassium in a gastric cancer patient by:(1) measuring an expression level of epidermal growth factor receptor (EGFR) in a biological sample obtained from the patient；(2) comparing the expression level of EGFR obtained in step (1) with a corresponding predetermined cut-off point； and(3) predicting that the patient is likely to sufficiently respond to chemotherapy when a tegafur, gimeracil, and oteracil potassium combination drug is used with an EGFR inhibitor, when the step (2) comparison reveals that the expression level of EGFR is greater than the cut-off point, or predicting that the patient is likely to sufficiently respond to chemotherapy when a tegafur, gimeracil, and oteracil potassium combination drug is used alone, when the step (2) comparison reveals that the expression level of EGFR is not greater than the cut-off point.
