To provide a composition useful for forming a heat conductive sheet that satisfies both high heat conductivity and sufficient softness, has sufficient cohesive strength at a surface portion of a heat conductive sheet and does not cause remaining paste and breakage of an electronic appliance when the sheet is peeled. The composition comprises (A) a photo polymerizable component consisting of a (meth)acryl type monomer or its partial polymer; (B) a heat conductive filler; (C) a photo reaction initiator for initiating the polymerization of the photo polymerizable component; and (D) a photo absorber for absorbing and removing a predetermined wavelength band from electromagnetic rays used for the polymerization of the photo polymerizable component.