PURPOSE: To make meet the horizontal positions of a sub-frame and a side member to each other in a structure where the sub-frame for mounting suspension is fastened below the side member being the structural member of a vehicle by enabling a bolt used for the fastening operation to have a positioning function.

CONSTITUTION: In a structure where a fastening bolt 5 penetrates a sub-frame from the downward to upward direction and screwed to a nut 2 provided at a side member 1, a female thread 4B for temporalily locking the bolt 5 to the sub-frame 3 is formed, and the screwed condition of the bolt 5 to the female thread 4B is released before the termination of the fastening.