A refiner includes a main body (1), a rotation shaft (2) provided inside the main body, a tapered rotor (3) attached to the rotation shaft with a space (3K) therein, a stator (4) provided in the main body, a rotor beating portion (31) provided on the rotor and having a groove between bars and through-holes, a stator beating portion (41) on the stator with a groove (M1) between bars (B1) and through-holes (H1), a raw material supply portion (11) for supplying a raw material into the main body, and a raw material discharge portion (5) for discharging a beaten raw material outside the main body. A portion of the raw material guided to a small-diameter opening portion (1H) of the rotor and the space of the rotor is beaten by passing through the through-holes of the rotor beating portion and the stator beating portion, and is discharged outside the stator beating portion from the through-holes of the stator beating portion.