Abstract: Provided is an injection-molding method for forming into given finished parts by injection-molding raw materials of a metal or ceramic powder feed, in which steps of coating a release agent to the mold, degreasing and freeze solidification are dispensed with. In this method, a metal or ceramic powder feed is kneaded with an agar sol comprising water, which may have or have not been treated magnetically, agar powders having a gel strength of 2000 g/cm.sup.2 at an least 2% concentration and sodium borate to form a clay form of sol-state plastic material, and this material is then put in a heat-retaining hopper of injection-molding equipment in which it is injection-molded. Alternatively, this clay form of plastic material is cooled for gelation and pelletization (to obtain finely granulated gels). The pellets are put in a hopper of injection-molding equipment in which it is formed while heated and melted.