A floor structure of a railcar includes: a pair of side sills extending in a railcar longitudinal direction; cross beams extending in a railcar width direction and coupling the pair of side sills; a supporting member, which is arranged on upper surfaces of the cross beams, in which bottom surface portions and convex portions projecting upward from the bottom surface portions are alternately, continuously formed in the railcar width direction, and which extends in the railcar longitudinal direction; receiving members located at positions corresponding to the cross beams, arranged on an upper surface of the supporting member, and extending in the railcar width direction; and a floor panel arranged on upper surfaces of the receiving members. The receiving members include: a floor plate contact portion that contacts the floor panel; and leg portions, extending from the floor plate contact portion to the bottom surface portion of the supporting member.