In a method of manufacturing a thermally conductive circuit board with high heat dissipation, high conductivity and high ground-connection, a sheet-like thermally conductive resin composition containing 70 to 95 wt. % inorganic filler and 5 to 30 wt. % thermosetting resin composition, a lead frame as a wiring pattern, and an electrically conductive heat sink with a metal pole placed therein are superposed, heated and compressed, and thus are combined to form one body. Consequently, a thermally conductive circuit board with a flat surface is obtained in which a grounding pattern is grounded to the heat sink inside the insulating layer. Thus, the grounding pattern and the heat sink can be connected electrically with each other in an arbitrary position inside the insulating layer of the thermally conductive circuit board. The method provides that a part of a lead frame and heat sink are connected not only mechanically, but also electrically, and allows an associated power module size to be reduced and its density to be increased.