An insulating plate (20) made of synthetic resin for transferring heat transferred from conductors to nuts (10) to a heat sink (40) is provided with nut accommodating recesses (21) for accommodating the nuts (10). Each nut accommodating recess (21) includes a bottom plate (22) to be sandwiched between the nuts (10) and the heat sink (40) and a surrounding wall (23) vertically extending from the bottom plate (22) to surround the side surface of the nut (10). The surrounding walls (23) are provided with first and second pressing surfaces (28, 29) to be pressed by ejector pins (83).