To obtain the subject composition capable of providing a tape exhibiting good thermal conductivity and tackiness at a temperature in practical use and simply separable when interposed between, e.g. plural members and laminated thereto by making the composition include a specific polymer and a tackifier, etc., as essential components.

This composition consists essentially of (A) at least one polymer of (i) a styrene-based elastic polymer and (ii) an olefinic elastic polymer, (B) a tackifier (preferably a terpenic tackifier or an alicyclic tackifier), (C) a softening agent (preferably a paraffinic oil) and (D) a thermal conductivity imparting agent (preferably alimina). Furthermore, the content of the component D is preferably set within the range of 5-90 wt.% based on the whole objective composition and the softening point is preferably ≤130°C. For example, a hydrogenated triblock copolymer of styrene-isoprene-styrene is preferably used as the component (i).