To selectively recover sodium formate effective as a raw material from a waste liquor rejected from a reactional step in the production of a hydrosulfite according to a sodium formate method.

A production waste liquor obtained by separating a hydrosulfite product from a reactional liquid and distilling off and recovering an alochol is electrodialyzed to thereby selectively recover the sodium formate and acid sodium sulfite. The resultant recovered liquid is then subjected to an oxidation treatment and further electrodialysis.