PURPOSE: To prevent foaming caused by aeration at the time of immersion process in which copper component is leached out from a copper raw material containing cuprous oxide in an aqueous sulfuric acid solution while being aerated, to produce a copper sulfate solution, by providing an immersion process preliminarily not using aeration.

CONSTITUTION: When the copper raw material containing cuprous oxide is subjected to leaching with the aqueous sulfuric acid solution to produce the copper sulfate solution, the copper raw material is immersed into the aqueous sulfuric acid solution and then the solution is agitated while it is aerated and a copper component in the copper raw material is leached with the aqueous sulfuric acid solution. As the leaching conditions, when the sulfuric acid concentration of the aqueous sulfuric acid solution is selected to 90-180g/l and the temp. is to ≤30°C, the leaching rate is preferably increased.