PURPOSE: To recover and re-utilize unreacted tert.-butylhydroperoxide by treating a reaction liquid containing epichlorohydrins synthesized from allyl chlorides and tert.-butylhydroperoxide using a substance in a reaction system.

CONSTITUTION: Residue after separating epichlorohydrins, tert.-butyl alcohol and unreacted allyl chlorides from a reaction liquid containing epichlorohydrins synthesized from allyl chlorides and tert.-butylhydroperoxide(TBHP) is subjected to azeotropic distillation together with water to separate unreacted TBHP and further unreacted TBHP is extracted and recovered from the distilled liquid by using allyl chlorides. A minute amount of water contained in allyl chlorides after extraction is subjected to azeotropic distillation together with allyl chlorides and recycled and re-utilized as a raw material to the above- mentioned azeotropic distillation system to treat epoxydation reaction liquid. Furthermore, the recovered TBHP has industrial value, since it can be re-utilized for the above-mentioned reaction.