PURPOSE: The titled casting material that is obtained by adding an organic filler to unsaturated polyester resin, thus undergoing scarce deformation of anode blades, even when the grinding speed is raised in processing magnetron anodes with a lathe and facilitating the removal of embedded materials after processing.

CONSTITUTION: An unsaturated polyester such as unsaturated alkyd resin obtained by polycondensation of 20W100mol% of unsaturated acid components and 80W0mol% of saturated acid components is combined with a polymerization inhibitor and dissolved in an ethylenic monomer. Then, the objective casting material is obtained by combining the resultant composition, preferably 30W70wt%, with an organic filler such as wood powder or pulp, preferably 70W30wt%, if necessary, a lubricant and a curing agent.