To provide a production method for polyoxyalkylene monools or polyols capable of easily removing a catalyst after reaction without generation of coloring or odor.

The production method for polyoxyalkylene monools or polyols comprises a step of processing at 100-180°C a polyoxyalkylene monool or polyol obtained by addition polymerization of (B) an alkylene oxide and (A) an active hydrogen group-containing compound in the presence of tetramethyl ammonium hydroxide and (C) a compound represented by general formula (1), [wherein R¹, R², R³ and R⁴ each independently are a 1-8C monovalent hydrocarbon group or hydrogen].