To provide a driving device of electric power steering, easy in assembling.

This driving device of the electric power steering includes a steering shaft, a motor part and a cylindrical housing 3 for storing these. In the driving device of the electric power steering, the housing 3 is constituted by connecting a cylindrical first housing 3A and a cylindrical second housing 3B, and is formed so that the steering shaft is inserted inside, and a metallic plate 4 larger than an inner diameter of the housing 3 is sandwiched between the first housing 3A and the second housing 3B, and a plurality of wiring boards 5 mounted with a switching element 51 are arranged on a main surface of the metallic plate 4, and are respectively electrically connected to the plurality of wiring boards 5, and a metallic body 64 electrically connected to a stator 22 on the side facing the stator 22, is fixed to a through-hole 41 in a state of being electrically insulated from the metallic plate 4.