The incidence of thyroid cancer is increasing rapidly in many countries, resulting in rising societal costs of the care of thyroid cancer. We reported that the active surveillance of low-risk papillary microcarcinoma had less unfavorable events than immediate surgery, while the oncological outcomes of these managements were similarly excellent. Here we calculated the medical costs of these two managements. We created a model of the flow of these managements, based on our previous study. The flow and costs include the step of diagnosis, surgery, prescription of medicine, recurrence, salvage surgery for recurrence, and care for 10 years after the diagnosis. The costs were calculated according to the typical clinical practices at Kuma Hospital performed under the Japanese Health Care Insurance System. If conversion surgeries were not considered, the 'simple cost' of active surveillance for 10 years was 167,780 yen/patient. If there were no recurrences, the 'simple cost' of immediate surgery was calculated as 794,770 yen/patient to 1,086,070 yen/patient, depending on the type of surgery and postoperative medication. The 'simple cost' of surgery was 4.7 to 6.5 times the 'simple cost' of surveillance. When conversion surgeries and recurrence were considered, the 'total cost' of active surveillance for 10 years became 225,695 yen/patient. When recurrence were considered, the 'total cost' of immediate surgery was 928,094 yen/patient, which was 4.1 times the 'total cost' of the active surveillance. At Kuma Hospital in Japan, the 10-year total cost of immediate surgery was 4.1 times expensive than active surveillance.