An ultraminiature sensor for thermal analysis is fabricated using micromachining technique and its fundamental characteristics are obtained. This device consists of monolithically integrated components of an air-bridge type microheater, a thin film thermocouple and a sample-holder. Boiling points of liquid samples, water and methanol, are clearly observed in the heating curve and the heating-rate curve, and sudden decrease of the temperature at the dropping time of the liquid sample without heating due to the effect of evaporation heat is also observed.