A vehicle deck structure that can suppress deformation of a deck floor is provided. The vehicle deck structure includes a deck floor that extends in a vehicle body front-rear direction and a vehicle width direction, a cross member disposed at a lower side of the deck floor and whose longitudinal direction corresponds to the vehicle width direction, and a top plate as a reinforcing member interposed between the deck floor and the cross member. The top plate has a plurality of ridges, whose longitudinal directions each correspond to the vehicle body front-rear direction, and which are arranged in parallel in a vehicle width direction, and these ridges overhang at both sides in the vehicle front-rear direction with respect to the cross member.