To enable visual inspection of the degree of wear on a liner in a housing of a screw conveyor.

A wear indicating member is embedded in the liner provided on the inner surface of a casing. The wear indicating member wears as the liner wear develops due to contact with a screw or the like, making its worn surface flush with the worn surface of the liner. The degree of wear development on the liner can thus be found out by the change of the worn surface as the wear develops.