To achieve efficient heat spreading and heat releasing by using a metal core of a circuit board, a terminal block includes an insulating block body and terminals. At least one of the terminals is provided with terminal portions for a connection with a circuit board. The terminal portions are inserted into respective through holes of the circuit board, the circuit board having a pattern circuit at a surface layer thereof and a conductive metal core at an intermediate portion in a thickness direction, so that heat of the metal core or of both the metal core and the pattern circuit is absorbed and transferred to the terminals. A bus-bar block includes an insulating block body and several parallel bus-bars with different lengths. Terminal portions at a tip end of the bus-bars are inserted, near heat-generating component on the circuit board, into the through holes of the circuit board.