To prevent generation of a rat hole in a hopper, generation of powder convection and segregation of metal powder; and to achieve uniformization of components of the metal powder and improvement of material yield by eliminating segregation of the metal powder, in a line for making sintered metal by mixing several kinds of metal powders, inputting the mixture into the hopper and automatically feeding the mixture into a molding machine.

A rectifying guide in which a conical pipe and a reverse conical pipe which is the conical pipe put upside down are integrated at the bottom surfaces of the cones, the inner portion of the conical pipe is hollow, and a several number of reverse triangular holes are formed on the inclination surface of the lower conical pipe is provided in the hopper. An insertion pipe which can be inserted into a hole of a powder feed pipe is integrated with the lower conical pipe of the rectifying guide. Accordingly, the powder flows radially toward the hopper wall surface in the upper cone and flows into the hollow portion of the lower conical pipe through the hole of the lower conical pipe, and thereby generation of a rat hole, convection and segregation of the powder are prevented.