To provide a spare tire support structure capable of functioning as a damper that exhibits a stable damping effect regardless of a change with time of a tire air pressure or a torque change of a bolt for fixing a tire.

The spare tire support structure 1, installed on an automotive floor panel 10, includes: a hollow bottomed cylindrical cushion receiving part 20 whose top end fixed on the floor panel 10 is open; a wheel receiving part 40 in which a support 41 for supporting a wheel portion 51 of a tire 50 is formed and a pressure portion 43 fitted in a cylinder of the cushion receiving portion 20 is formed on a rear surface of the support portion 41; an elastic body 30 sandwiched between the pressure portion 40 and the cushion receiving portion 20; and a fastening nut 60 for fixing the wheel portion 51 on the wheel receiving portion 40. The wheel receiving portion 40 supports the tire 50 so as to be in no contact with the tire portion 52 of the tire 50 and to be in a no-contact state between the floor panel 10 and the tire portion 52.