<p>A process for producing an ether (co)polymer in which molecular-weight regulation is easy and the post-treatment of a liquid reaction mixture after polymerization (solvent recovery, etc.) is easy. The process for ether (co)polymer production is characterized by polymerizing an ether monomer in a solvent in the presence of both a catalyst comprising a condensate of an organotin compound with an alkyl phosphate and a chain-transfer agent comprising as a major component an aliphatic polyhydric alcohol represented by the following general formula to thereby produce an ether (co)polymer. C<SUB>x</SUB>(OH)<SUB>y</SUB>H<SUB>z</SUB> In the formula, X is an integer of 2-8; Y is an integer of 2 to (2X+2); Z is an integer of (2X+2-Y); and the hydroxy groups are bonded in any positions.</p>
