Temperature measurements of the graphite divertor plates have been made in the high-power heating experiments of JT-60 using thermocouples inserted in the graphite tiles. A total heating power of 30 MW and a total absorbed energy of 90 MJ were achieved in the divertor operation with line-averaged electron density ne = (2.5–6)×1019 m−3. The larger temperature rise was observed in the discharges with lower ne compared to higher ones. The temperature rise on the ion side was higher than that on the electron side at low ne by a factor of 3. However, a significant reduction of the temperature rise was observed on the ion side with increasing ne, while that on the electron side was moderate. A considerable increase of the neutral pressure in the divertor chamber was also observed with increasing ne. The estimated peak heat flux during the additional heating with a total absorbed power of 24 MW in low density discharges was roughly 20 MW/m2 on the ion side. The ratio of total heat deposition on the divertor plates to the absorbed energy was changed from 45 to 25% with increasing ne. After the experiments, erosion was observed at the edge of the thermocouple-mounted graphite tile attached on the electron side.