To provide a spare tire fitting structure capable of reducing vertical vibration of a floor panel and reducing booming in a cabin.

In a spare tire fitting structure, the central part 5a of a spare tire 2 is fixed to a floor panel 1 of a vehicle by a fixing member 6. The fixing member 6 has a low rigidity part 9 having the rigidity in the vehicle width direction lower than that in the longitudinal direction of the vehicle between the spare tire 2 and the floor panel 1. Only the roll resonance frequency of the spare tire 2 is lowered to make the roll resonance frequency close to the bounce resonance frequency. In the roll resonance, both end parts 2a, 2b of the spare tire 2 opposite to each other taking the central part 5a of the spare tire 2 as the center vibrate in the reverse phase in the vertical direction of the vehicle, so that the vibration in the vertical direction of the vehicle of both end parts 2a, 2b caused by bounce resonance can be reduced to restrain vertical vibration of the floor panel 1.