A process for producing a polyether having at least one hydroxy group by subjecting a cyclic monomer to ring-opening addition polymerization to an initiator having a hydroxy group in the presence of a double metal cyanide complex catalyst, comprising the following steps: initial step: supplying the cyclic monomer in an amount of 5 to 20 mass percent of the initiator to a reaction system containing the initiator and the catalyst, to carry out reaction, wherein the reaction system temperature when supply of the cyclic monomer is started is from 120 to 165° C., and the maximum temperature of the reaction system after supply of the cyclic monomer is higher by from 15 to 50° C. than the temperature when supply of the cyclic monomer is started; and polymerization step: supplying the cyclic monomer to the reaction system after the initial step to carry out ring-opening addition polymerization.