Electrical properties of W-doped KNbO3 ceramics were studied by combining their diffuse reflectance measurements. In the case of samples sintered in a reducing atmosphere, CH4/Ar=1/99, they were conductive and two step of positive temperature coefficient of resistivity (PTCR) effects were observed at temperatures where ferroelectric phase transitions from orthorhombic to tetragonal (Tr) and successively to cubic (Tc) occurred, while the resistivities higher than 106Ωcm were observed for those sintered in air. The 0.2mol% W-doped sample sintered in the reducing atmosphere showed room-temperature resistivity of 101-102Ωcm, with PTCR jump (Log Rmax/Rmin) of about 1.4 order of magnitude. Diffuse reflectance measurements for the samples sintered in the reducing atmosphere also indicated an increase of the conduction electron concentration with increasing doped amount of W.