An electric power steering apparatus can improve heat dissipation of a power
board.
A heat sink is mounted on the power board in surface contact therewith, on which
power board there is mounted a bridge circuit including a plurality of semiconductor
switching elements for switching an electric current supplied to an electric motor
in accordance with torque assisting a steering wheel. The heat sink has a plurality
of protrusions formed on a surface thereof at a side opposite to the power board.