The present invention provides a solid-phase support which has both high hydrophilicity and excellent pressure resistance. The solid-phase support is characterized by containing a resin that has a divalent to tetravalent structure represented by formula (1). (In formula (1), R1 represents an n-valent organic group; each X1 independently represents a divalent group represented by formula (2), or the like; and n represents an integer of 2-4.) (In formula (2), R2 represents a divalent hydrocarbon group having 1-2 carbon atoms; and Y1 represents a thio group, a sulfinyl group, an oxy group or an imino group.)