There is provided a method for easily determining an undifferentiated state of pluripotent stem cells without relying on the judgment of a skilled technician. The method includes: a step of evaluating an undifferentiated state of pluripotent stem cells based on a time-dependent change in a variation value of an extracellular metabolite contained in a culture medium in which the pluripotent stem cells are cultured, wherein the extracellular metabolite is at least one selected from a group consisting of L-glutamic acid, L-alanine and ammonia.