Abstract: A heat conductive molded body effectively radiating heat generated from semiconductor elements, power supply or light source used for electric apparatuses, and a manufacturing method thereof and a semiconductor device excellent in heat radiation. A heat conductive molded body, wherein a diamagnetic filler having a thermal conductivity of 20 W/m·K or more is orientated in a fixed direction in high polymer, a manufacturing method of the heat conductive molded body, wherein a magnetic filed is applied to high polymer composition containing the diamagnetic filler, and the diamagnetic filler contained in the composition is orientated and hardened in a fixed direction, and a semiconductor wherein said heat conductive molded body is interposed between a semi-conductor element and a heat conductive member.