There is provided a a sustained release preparation including a dispersion for a sustained release preparation and a volatile active substance, the dispersion having viscosity at 25° C. of not more than 100 mPa·s and including polymer particles which are obtained by polymerizing ethylenically unsaturated group-containing monomers (A), polyvinyl alcohol (C1) in an amount of more than 0% by weight but not more than 30% by weight relative to a total amount of the ethylenically unsaturated group-containing monomers (A), having a degree of saponification of more than 82 mol % but not more than 91.5 mol %, polyvinyl alcohol (C3) in an amount of more than 0% by weight but not more than 30% by weight relative to the total amount of the ethylenically unsaturated group-containing monomers (A), having a degree of saponification of not less than 98 mol %, and water.
