A silicon purification method includes: loading a base material that is a starting material made of metallic silicon into a graphite crucible, heating and melting all of the base material which is disposed in an acidic inert gas atmosphere, maintaining the molten base material in the graphite crucible, and thereby oxidatively purifying the base material; loading the oxidatively-purified base material into a water-cooled crucible, gradually solidifying the base material after the base material disposed in a high vacuum atmosphere is fully molten, and thereby removing an unsolidified portion; and fully melting the base material which is disposed in a high vacuum atmosphere and in which the unsolidified portion is removed, and maintaining the base material in the water-cooled crucible.