A blade member has a shaft portion connected to a rotating shaft, and a blade plate portion projecting from the shaft portion toward an outer peripheral wall of a container. The blade plate portion has a plane-like configuration without being formed with a through-out portion, and extends in an up-and-down direction along the shaft portion. The blade plate portion has a projection portion, at a tip end side apart from the shaft portion, projecting upwardly. A top portion of the projection portion is non-edge surface without being formed with an angled portion.