Piezoelectric properties of potassium niobate (KNbO3; KN) crystal grown using the Vertical Bridgman method were obtained by a resonance-antiresonance method for a length extensional mode. The crystal was poled at 200°C under an electric field of 70 V/mm applied parallel to one of the spontaneous polarization axes. An electromechanical coupling factor (k31) of 0.248, mechanical quality factor (Qm) of 5700, piezoelectric constant (d31) of 9.6 pC/N, elastic compliance (s11E) of 4.02 pm2/ N, and constant (e33T/e0) of 42 were obtained. The optical absorption coefficient of poled crystal has been less than 1.0 cm-1 in the wavelength region of 400-1600 nm. Comparing these values with the reported one for TSSG-KN, indicated that our VB-KN was of good quality.