Methods and apparatus for manufacturing high purity polysilicon. The apparatus includes a vacuum chamber; first and second electron guns disposed at an upper side of the vacuum chamber to irradiate electron beams into the vacuum chamber; a silicon melting unit which is placed on a first electron beam-irradiating region corresponding to the first electron gun and to which powdery raw silicon is fed and melted by the first electron beam; and a unidirectional solidification unit placed on a second electron beam-irradiating region corresponding to the second electron gun. The unidirectional solidification unit is provided therein with a start block driven in a downward direction to transfer molten silicon in the downward direction and is formed at a lower side thereof with a cooling channel. The start block includes a dummy bar having a silicon button joined to an upper portion of the dummy bar.