The present invention provides a production method of a hydroxyl-containing polymer including: protecting a hydroxyl group of a hydroxyl-containing monomer with a protecting group to make the monomer a protected monomer with decreased hydrophilicity; adding the protected monomer alone or together with a hydrophobic monomer to a water-based medium containing a salt and a dispersion stabilizer; adding a polymerization initiator to the mixture to carry out suspension polymerization; and de-protecting the obtained polymer having the protecting group to recover the hydroxyl group.