The present invention relates to a support for solid-phase synthesis, which contains a porous copolymer particle, the copolymer particle containing 25 to 60% by weight of an aromatic-vinyl structural unit, 20 to 55% by weight of a vinyl cyamide structural unit, 5 to 18% by weight of an ethylenically-unsaturated-carboxylic-acid structural unit, and 2 to 15% by weight of an aromatic-divinyl structural unit. The support according to the invention fluctuates little in the degree of swelling depending on the kind of the organic solvent in contact therewith.