To provide a steering support beam structure which prevents dimensional accuracy from being degraded due to welding, and obtains sufficient stiffness strength without making the outer diameter of the steering support beam larger than it is necessary.

Diameter contracted parts 23, each of which is smaller than the inner diameter of its intermediate part 21, are provided for both the right and left ends of an outer pipe 20, and diameter expanded parts 13, each of which is larger than outer diameter of its intermediate part 1, are provided for both the right and left ends of an inner pipe 10. Since the inner diameter of the intermediate part 21 of the outer pipe 20 is larger than the outer diameter of the diameter expanded part 13 of the inner pipe 10, the diameter expanded part 13 of the inner pipe 10 passes through with ease the inside of the intermediate part 21 of the outer pipe 20, the inner pipe 10 is thereby excellent in assemblage, and since a steering support beam 30 is structurally formed out of double pipes composed of the inner pipe 10, and of the outer pipe 20, it is prevented from warping at the time of welding, and concurrently, its sufficient stiffness strength can thereby be secured.