A primer composition which is particularly effective to strongly bond fluorosilicone rubbers to metal, plastics, fibers, and the like, comprising(A) 100 parts by weight of a polyorganosiloxane represented by formula (I): ##EQU1## wherein R.sup.1 represents a substituted or unsubstituted monovalent hydrocarbon group, 10 to 50 mol % of the hydrocarbon groups of R.sup.1 being perfluoroalkyl and 0.01 to 1.0 mol % of the hydrocarbon groups of R.sup.1 being vinyl, and a is a number of from 1.98 to 2.01, and which has a viscosity as measured at 25.degree. C. of 1,000,000 cSt or more;(B) 5 to 100 parts by weight of a silica filler;(C) 0.5 to 50 parts by weight of a compound represented by formula (II): ##STR1## wherein X represents an organosilicon-containing group or a hydrocarbon-containing group, R represents methyl or hydrogen, and n is an integer of 1 or larger; and(D) an organic solvent.