We have measured the Seebeck coefficient and power factor of single crystalline β-FeSi2 grown by a temperature gradient solution growth (TGSG) method using Ga and Zn solvent. Typical resistivity and carrier density at 300K were 0.03 Ωcm and 2×1019Cm-3 for p-type and 0.2 Ωcm and 5×1018 cm-3 for n-type crystals, respectively. The Seebeck coefficient measured along  direction was approximately 350 μV/K(p-type) and -700 μV/K(n-type) at 300K and showed a maximum value of 500 μV/K(p-type, T=∼25K) and 2100 μV/K(n-type, T=∼70K). The maximum power factor was 4.2 × 10 -6 Wcm-1K-2 (p-type, 7=170K) and 23 × 10-6 Wcm-1K-2 (n-type, P=100K). The value was more than one order of magnitude larger than that of previously reported.