The electrical conductivity of highly pure polycrystalline sample of $La_2O_3$ has been measured at temperatures from $600^{circ}C$ to $1,050^{circ}C$ and oxygen pressure range of $1{ imes}10^{-6}$ torr to $1{ imes}10^2$ torr. The defect structure and semiconductor type are investigated by measuring the temperature and oxygen pressure dependences of electrical conductivity. Sintered $La_2O_3$ exhibits the electrical conductivities in the range of $1{ imes}10^{-9};to;1{ imes}10^{-3};ohm^{-1}{cdot}cm^{-1}$ under the above oxygen pressures. The oxygen pressure dependences on electrical conductivity are characterized by 5.3 at $1,000^{circ}C$ and 5.7 at $700^{circ}C$ and more higher values of 9∼14 below $700^{circ}C$. The increase in n value with decreasing temperature indicates that a simple conduction mechanism does not exist in this material. The conduction carriers are not metal vacancy but oxygen ion at lower pressures. The conduction data indicate a significant ionic conduction at lower temperatures and electronic conduction at higher temperatures.