To obtain a torsion beam type suspension in which the number of component items is reduced, a welding length can be shortened and reduction in weight is attained.

Notches 22 corresponding to the cross-sectional shape of a trailing arm 2 are formed at both end sides of a torsion beam 4. Each of the notches 22 has an opening 24 in the radial direction of the trailing arm 2, and the trailing arm 2 includes a joint position where the torsion beam 4 is welded to the trailing arm 2 to be coupled, and an inserting position where the trailing arm 2 can be inserted from the radial direction of the trailing arm 2 through the opening 24 of the notch 22. At the joint position, the outer circumference of the trailing arm 2 inserted into the notches 22 is surrounded by semiperimeter or more with the torsion beam 4 and at the joining position, the opening 24 is formed in such a size that the trailing arm 2 can not be inserted into the opening 24 of the notch 22 from the radial direction of the trailing arm 2. At the inserting position, the trailing arm 2 is inserted from the opening 24 of the notch 22, then moved in an axial direction, and welded and coupled at the joint position.