Thermoelectric properties of the polycrystalline (Bi_(0.2)Sb_(0.8))₂Te₃, fabricated by mechanical alloying and hot-pressing, were investigated with addition of BN as scattering centers. The Seebeck coefficient of the hot-pressed (Bi_(0.2)Sb_(0.8))₂Te₃ was not affected by addition of BN. The thermal conductivity of the hot-pressed (Bi_(0.2)Sb_(0.8))₂Te₃ decreased with increasing the volume fraction of BN due to the reduction of k_(el) However, the lattice thermal conductivity k_(ph) was little varied with addition of BN. The figure-of-merit of the hot-pressed (Bi_(0.2)Sb_(0.8))₂Te₃ was 3.05×10^(-3)/K without addition of BN and was lowered with increasing the volume fraction of BN, because the increase of the electrical resistivity was larger than the reduction of the thermal conductivity due to the grain refinement.