A power steering system for a vehicle includes a torque sensor, an electric motor operated according to a detected value detected by the torque sensor, and a power transmission mechanism for transmitting rotational power of the electric motor to the side of a steering wheel or wheels. The power steering system makes it possible to protect the electric motor while reducing the weight through simplification of the vehicle body component members. A cross member that is bent to form a recessed portion is provided in the vehicle body. At least an electric motor of the power steering system is disposed inside the recessed portion. However, the torque sensor, the electric motor and a power transmission mechanism can be disposed inside the recessed portion.