The present invention relates to a process for producing of polycrystalline silicon, and the method includes (1) preparing a silicon-containing gas; (2) storing the silicon-containing gas in a storage tank; (3) depositing polycrystalline silicon by injecting the silicon-containing gas stored in the storage tank to a CVD reactor; (4) treating an off-gas emitted in the depositing step; and (5) injecting the gas treated in the treating step to the storage tank.