Pool nucleate boiling heat transfer experiments were performed for water at 0.101 MPa to examine the elementary process of the nucleate boiling. Heat transfer surface was made from a copper printed circuit board. Direct current was supplied to heat it up. The Bakelite plate of the backside of a copper layer was taken off at the center portion of the heat transfer surface. The instantaneous variation of the backside temperature of the heat transfer surface was measured with an infrared radiation camera. Bubble behavior was recorded with a high speed video camera. In the isolated bubble region, surface temperature was uniform during waiting time. When boiling bubble generation started, a large dip in the surface temperature distribution was formed under the bubble. After the bubble left from the heat transfer surface, the surface temperature distribution returned to former uniform distribution. Surface temperature was not affected by the bubble generation beyond 1.8 mm from the center of the bubble. In the intermediate and high heat flux region, the variation of surface temperature and heat flux did not become large even though the heat flux increased. The heat flux variation was close to that at the isolated boiling region.