Disclosed are a purification device as well as a purification method of solar-grade polysilicon, relating to a polysilicon, which provides a purification device and a purification method of solar-grade polysilicon characterized by low cost, high purity, simple process, easy operation and suitability for large-scale production. The purification device is equipped with a vacuum system, a melting system and a directional solidification system; wherein the vacuum system is provided with a mechanical rotary vane pump, a lobed element pump and an oil diffusion pump, and the melting system is provided with a vacuum chamber, a secondary feeder, an observation window, a rotary ventilation device which can be raised and lowered, an induction coil and a graphite crucible; and the directional solidification system is disposed at the lower part of the vacuum chamber and is equipped with an electric resistance-wire heating and holding furnace, a graphite mold, a holding furnace frame, a water-cooled copper tray and an elevating lever which can control speed. The metal silicon is treated by induction heating to be molten, the oxidizing gas is fed under conditions of low vacuum and high temperature to remove boron, and then under conditions of high temperature and high vacuum to remove phosphorus, and finally the molten silicon solution is poured into a directional mold to strictly conduct directional solidification to remove metal impurities.