An insulating film material for plasma CVD of the present invention is constituted of a silicon compound including two hydrocarbon groups bonded to each other to form a ring structure together with a silicon atom, or at least one branched hydrocarbon group, wherein within the branched hydrocarbon group, α-carbon that is a carbon atom bonded to the silicon atom constitutes a methylene group, and β-carbon that is a carbon atom bonded to the methylene group or γ-carbon that is a carbon atom bonded to the β-carbon is a branching point.