We herein report a case of type B insulin resistance in which the therapeutic efficacy was evaluated by intermittent scanning continuous glucose measurement (isCGM). A 55-year-old Japanese man was diagnosed with type B insulin resistance and systemic scleroderma based on the presence of concomitant hyperglycemia and hyperinsulinemia, positivity for both anti-insulin receptor antibody (anti-IRAb) and anti-U1-ribonucleoprotein antibody, and specific physical findings. Treatment for hyperglycemia with an α-glucosidase inhibitor and glucagon-like peptide-1 receptor agonist was unsuccessful; immunosuppressive therapy with prednisolone and cyclosporine was therefore initiated. Between days 15 and 32 of immunosuppressive therapy, the serum immunoglobulin G level, fasting blood glucose (FBG) level, anti-IRAb inhibition rate, and average daily glucose concentration sequentially began to decrease. Finally, on day 41, the patient tested negative for anti-IRAb. During treatment, isCGM showed diurnal variation in blood glucose levels. Before the introduction of immunosuppressive therapy, the FBG and blood glucose levels after breakfast decreased, and the blood glucose levels fluctuated markedly between 0 and 8 AM. After the introduction of immunosuppressive therapy, the daily fluctuation in the blood glucose levels decreased. In this case, long-term isCGM was useful for determining the efficacy of immunosuppressive therapy.