PURPOSE: To easily provide the subject economical aqueous solution harmless when administered to living bodies.

CONSTITUTION: High-purity water or alkaline ionic water and an organic acid are added to germanium dioxide followed by heating and then neutralizing the mixture with an acid-neutralizing agent, thus obtaining the objective weakly acidic or weakly alkaline aqueous solution. In the neutralizing process, when the high-purity water or alkaline ionic water and acid-neutralizing agent are added to the above mixture repeatedly by small amounts under agitation while heating, the objective solution can be produced within a shorter time.