To improve performance by enhancement of a hulled ratio and to simplify constitution.

An immature grain winnowing machine (B) is disposed in a fore process step of a hulling and winnowing machine (A) and, after the immature grains in paddy are separated and removed by the immature grain winnowing machine (B), the immature grains are hulled and winnowed by the hulling and winnowing machine (A). The grains from which the immature grains in the paddy are separated and removed by the immature grain winnowing machine (B) are hulled and winnowed by the hulling and winnowing machine (A) and are separated to two kinds; mixed rice composed of unpolished rice and paddy and dust such as chaff. In this case, the immature grain winnowing machine (B) is arranged above the hulling and winnowing machine (A), by which both machines are integrally constituted.