Semiconductive La-doped BaSnO₃ with a perovskite-type structure was prepared at relatively low temperatures using a polymerized complex method. The Ba-, La-, and Sn-citrate complexes polymerized randomly with citric acid and ethylene glycol were synthesized and then pyrolyzed to form amorphous precursor. The perovskite-type single phase of La-doped BaSnO₃ was directly obtained by heating the amorphous precursor at 873 K, owing to the homogeneous distribution of constituent elements Ba, La, Sn on an atomic scale in the polymerized complex. The electrical conductivity σ and Seebeck coefficient S were measured in the temperature range 373∼1073 K for the bulk sample to evaluate the thermoelectric properties. The Ba_0.95La_0.05SnO₃ showed n-type degenerate semiconducting behavior and the thermoelectric power factor S²σ increased from 6.5×10⁻⁸ Wm⁻¹K⁻² to 1.0×10⁻⁶ Wm⁻¹K⁻² with increasing temperature.