A new electric furnace has been designed and fabricated for measurements of the high-resolution synchrotron radiation powder diffraction profiles from materials at high temperatures up to 1807 K in air, suitable for the multiple-detector system installed at the BL-4B(2) experimental station of the Photon Factory, Tsukuba, Japan. In the present study, at 1703 K in air, the whole powder pattern of National Institute of Standard and Technology ceria powder was step scanned at a step interval of 0.004 degrees in 2 theta, by the counting time of 1.5 s/step and with a monochromatized 1.205363(5) angstrom X-ray, in just 7 h. The full width at half-maximum of the 111 reflection of the ceria was narrow (0.0139 degrees). The delta d/d resolution of the ceria ranged from 0.058% to 0.126% at 1703 K, where d and delta d are the lattice spacing and peak width, respectively. Precise unit-cell parameter 5.51259(1) angstrom and the atomic displacement parameters were refined by the Rietveld analysis of the powder data measured at 1703 K. An electron-density map of ceria at 1703 K was obtained by the maximum-entropy method.