In this study, heating tests on ring-restrained specimens were conducted by using a small cylindrical electric furnace to evaluate the risk of high-temperature fire spalling in high-strength concrete at an early age. Early age was defined as the period up to approximately one month of age at which the design basis strength was developed. The ages of the specimens used for the heating tests were 4, 9, 24, and 43 days. The measured parameters were the internal temperature, vapor pressure, and restraint stress. The tensile strain at the time of fire spalling was calculated to evaluate thermal-stress-induced fire spalling. The results showed that fire spalling occurred at all ages, but the size of fire spalling was small in the early stage of aging and increased as the age of specimen increased. The tensile strain at the early age of the material was found to increase with the age of the specimen. Thus, the presence or absence and degree of fire spalling can be determined by evaluating the tensile strain.