The present invention provides a production process, in which, when an
ethylene oxide copolymer is obtained, conditions for obtaining this
copolymer having a desirable molecular weight with ease and good
reproducibility are provided. The production process for an ethylene oxide
copolymer, according to the present invention, comprises the step of
carrying out polymerization of a monomer mixture under stirring in a
solvent, thereby obtaining the ethylene oxide copolymer, wherein the
monomer mixture includes ethylene oxide and a substituted oxirane compound
of a structural formula (1) as essential raw materials; with the
production process being characterized in that the stirring is carried out
by a stirring power of not less than 0.6 kW/m.sup.3.
