Provided is a silicone anti-foaming agent composition that not only has superior anti-foaming speed but also in which anti-foaming performance is not reduced even when used repeatedly or over a long period. The composition comprises: a polyorganosiloxane polymer crosslinked product having a polyoxyalkylene group, which includes: moiety structure (I): -R1-(R22SiO)d-R1(where R1 represents an alkylene group bonded to a silicon atom on the polysiloxane chain, R2 represents a monovalent hydrocarbon group, and d is 200 to 1000); and moiety structure (II): —(CeH2e)—O—(EO)x-(PO)y-(BO)z-R3 (where a single bond on the left end is bonded to a silicon atom on the polysiloxane chain, R3 represents a hydrogen atom, an alkyl group, an aryl group or an acyl group, e is 2 to 10, (x+y+z) is 40 to 100, x is 15 to 50, y is 15 to 50, and z is 0 to 50).