A synthetic resin foam is applied to an outer or inner peripheral surface reinforcing member such as a steering hanger member made of a steel pipe and secured to a vehicle body of an automobile to reinforce the vehicle body. The steering hanger member includes hanger beams made of a steel pipe and connected to left and right front pillars of the vehicle body. Thus, it is possible to obtain a reinforcing member structure for the vehicle body at a low cost, which is capable of effectively enhancing the rigidity of the reinforcing member, while suppressing an increase in weight to the utmost.