This epoxy group-containing cyclic organosiloxane represented by formula (1) includes at least two epoxy groups in a single molecule, and thus has excellent compatibility with other organic resins when prepared into a composition with a compound including an organic group that is reactive with said functional groups, and also exhibits a function as a binder. The epoxy group-containing cyclic organosiloxane also includes a hydrolyzable silyl group, and can thus also be expected to be effective as a silane coupling agent. (R1 is an alkyl group or an aryl group; R2 is a hydrogen atom or an alkyl group that may have a substituent selected from a halogen atom, a vinyl group, an epoxy group, a thiirane group, a (meth)acrylic group, a mercapto group, an iso(thio)cyanate group, a hydrolyzable silyl group, a succinic anhydride group, a perfluoroalkyl group, a polyether group, and a perfluoropolyether group, wherein there is at least one R2 including a hydrolyzable silyl group as a substituent and at least two R2s including an epoxy group as a substituent; and n is an integer of from 3 to 6.)
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