PURPOSE: To obtain high purity molybdenum powder having very low mixing content of impurities, such as radioactive material, by using MoO3 as the initial raw material, adding iron ion to solution dissolved with aqueous ammonia, making deposit of iron hydroxide and depositing the radioactive material together with the above.

CONSTITUTION: The solution dissolving MoO3 into the aqueous NH4OH and the iron ion solution are mixed to make the deposit of the iron hydroxide and deposit U and Th together with this. Filtrate filtering and separating this deposit is acid-decomposed by using hydrochloric acid or nitric acid to generate deposit of a first H2MoO4. Successively, this deposit is extracted and washed at about three times and after removing almost quantity of heavy metal kind and a large part of alkali metals, again this is dissolved with the aqueous NH4OH and the same treatment as the previous process is repeated to obtain a secondary H2MoO4 having high purity as the deposit. Further, the filtrate of the solution dissolving this into the aqueous NH4OH is cooled to generate crystal of ammonium molybdate and this is reduced to make MoO2 and this is further reduced to obtain the aimed Mo powder.