A wheeled luggage with expandable body has two support mechanisms each comprising a sliding board secured to the side of auxiliary body, a locking mechanism secured to the side of main body and comprising two opposite locking members each having a ratchet member, and a trigger mechanism comprising a plate member, a trigger member, and two sliding members. In an unused position, the width of a flexible section is reduced to a minimum by closing the zipper and the sliding member is engaged with the rear tooth of the ratchet member, thereby preventing the sliding board from forward moving. The width of the flexible section is increased to a maximum by opening the zipper in a use position. The plate member is pushed rearward for disengaging the sliding members from the ratchet members, thereby permitting a rearward sliding of the sliding board from the use position to the unused position.