PURPOSE: To obtain a difficultly evaporable polyester resin having excellent storage stability by mixing an ethylenically unsaturated polyester with styrene, a paraffin and pyrogenic silicic acid having a hydrophilic terminal group and a hydrophobic terminal group.

CONSTITUTION: This resin comprises an ethylenically unsaturated polyester (including a vinyl ester) (A), styrene (B) as a comonomer, 0.01-2 wt.%, based on total of components A and B, paraffin (C) as a preventive against the evaporation of component B, desirably a mixture of a solid one with a liquid one, especially a mixture of a solid one, especially a mixture of one having a melting point of 25-50°C with one having a melting point of 51-100°C, and 0.004-0.4 wt.%, based on the total of components A and B, pyrogenic silicic acid (D) having 10-90% hydrophilic SiOH terminal groups and 90-10% hydrophobic SiR terminal groups (wherein R is a 1-4C alkyl, desirably methyl).