A floor body for a vehicle may include a floor panel forming a lower portion of a vehicle, side sill members extending in a length direction of the vehicle and coupled to both sides of the floor panel, a center side area being a virtual area with a shape extending in a length direction on the floor panel and passing through a point at which a center side member extending in the length direction of the vehicle from both sides of a central portion of the floor panel is provided, and a cross member disposed on the floor panel and extending in a width direction of the vehicle to pass through the center side area and formed so that a portion of the cross member positioned outside the center side area is thicker than that of a portion of the cross member positioned in the center side area.