In order to investigate the details of an atomic configuration in metals and alloys, a precise electrical resistance measurement apparatus at high temperatures was constructed. Accuracy of temperature control is found to be 0.01 "C at around 300 "C, and the accuracy of the electrical resistivity measurement is 0.01 nfl cm for an aluminum sample which has an electrical resistivity of 6X103 nR cm at around 300 "C. Using the apparatus, thermal generation of a vacancy at 320 "C in a highly perfect aluminum crystal was detected. 0 1995 American Institute of Physics.