To solve a problem in a conventional screw feeder wherein since gravity load of carried powdery bodies etc. is applied to a rotating shaft to bend it, a bar-shaped portion of a shaft end is moved violently like a precessional motion during rotation, causing considerable early wear of a seal member.

In this rotating shaft seal mechanism for a screw feeder, a bearing mechanism and a seal mechanism are provided in an end part of a rotating shaft of the screw feeder incorporated into a casing protruded from the casing to be located in positions shifted from each other. The rotating shaft seal mechanism is constituted by concentrically superposing a seal member brought into contact with the rotating shaft on a flexible displacement absorbing member positioned outside the seal member within a seal housing mounted to the outer side of the casing.