A first reference position C1 constituting a middle point is calculated by measuring positions of left and right damper attaching holes 22 in a white body 12. A second reference position C2 constituting a middle point is calculated by measuring positions of left and right hubs 44 in a suspension assembly 20. A position of the suspension assembly 20 is adjusted by a slide table 56 such that the first reference position C1 and the second reference position C2 are coincident with each other. The suspension assembly 20 is moved up by a lift mechanism 59 and is attached to the white body 12.