PURPOSE: To easily and safely dispose tractor members in a two-story parking device for parking automobiles on upper and lower stories and to dispose the tractor members on both sides of each post as required, relating to a post structure disposed to support automobile-parking pallets in such a way that the pallets are freely raised and lowered.

CONSTITUTION: A first post member 53 which comprises a U-shaped portion 57 of U-cross section on one side of which a reinforcing portion 59 is formed projecting almost parallel to the bottom surface of the U-shaped portion from one open end of the U-shaped portion, and a second post member 55 that forms line symmetry with the first post member with respect to the bottom face of the U-shaped portion, are joined together on the bottom surface of the U-shaped portion. A reinforcing member 65 is bridged in position between the reinforcing portion 59 of the first post member and the reinforcing portion of the second post member, and the first and second post members are each formed by bending a plate.