An electric power steering apparatus capable of being both lightweight and rigid. A lightweight electric power steering apparatus is achieved wherein a gear housing (45) that houses an electric assist mechanism, a lower support bracket (54) for fastening the gear housing (45) to the vehicle body, a sensor housing (56) that houses a torque sensor (57), an outer column (30) of a steering column (6c), and an upper support bracket (59a) for fastening the middle section of the outer column (30) to the vehicle body can all be integrally formed of synthetic resin, improving the strength of the joined sections of these members.