A floor panel has: a floor panel main body whose central portion and both outer side portions in a vehicle transverse direction are joined together, and that is formed by plural plate members being joined together at the central portion and the both outer side portions in the vehicle transverse direction. Among the second joining portions, a position of a central joining portion at the central portion in the vehicle transverse direction of the floor panel main body is offset in the vehicle longitudinal direction with respect to positions of outer side joining portions at the both outer side portions in the vehicle transverse direction of the floor panel main body. A different-type member joining portion, which is formed by plate members being joined together, is provided at at least one of the central portion, one of the outer side portions, and another of the outer side portions.