This paper proposes a vital data measurement system during exercise using a thermoelectric element as a power supply. In recent years, energy harvesting techniques have been attracting attention. Powers saving sensors driven by energy harvesting techniques are expected to eliminate maintenance such as battery replacement. A thermoelectric element is an energy harvesting device. The thermoelectric element generates power if there is a temperature difference. However, thermoelectric element usefulness is limited, because the thermoelectric element requires a large temperature differential to obtain a sufficient power. Accordingly, we considered a new practical use of the thermoelectric element. In this study, we drive the microcomputer by using the thermoelectric element attached to the person during exercise.