A lower body for a vehicle includes front and rear main bodies each including pipes, a pair of first longitudinal members extending in a forward/rearward direction and spaced apart from each other in a transverse direction, a first transverse member extending in the transverse direction and connecting the first longitudinal members, and mounting parts each having an outer side to which the first longitudinal members and the first transverse member are coupled, and a pair of lower body main members connecting the outer sides of the mounting parts and two opposite sides of upper ends of the front and rear main bodies spaced apart from each other, the pair of lower body main members each having a pipe shape and extending forward and rearward to constitute upper side members of the front and rear main bodies and defining an overall length of the vehicle.