A folding piece of luggage including: - parallel first and second rigid panels (2, 3); - third and fourth rigid panels (6, 7), each of which is mounted on and articulated to one of the first and second panels (2, 3) between a deployed position in which said third or fourth panel (6, 7) extends between said first and second panels (2, 3), perpendicularly to said first and second panels (2, 3), and a retracted position in which said third or fourth panel (6, 7) extends parallel to said first and second panels (2, 3); the third and fourth panels (6, 7) defining with the first and second panels (2, 3) a rigid frame when the third and fourth panels (6, 7) are in their deployed position; - fifth and sixth panels (4, 5) each of which connects the first and second panels (2, 3) and that define with the first, second, third and fourth panels (2, 3, 6, 7), when the third and fourth panels (6, 7) are in their deployed position, an internal storage space of parallelepipedal shape; the fifth and sixth panels (4, 5) being deformable in a direction x perpendicular to said first and second panels (2, 3) between an unfolded position and a folded position so that, when the third and fourth panels (6, 7) are in their retracted position, the first and second panels (2, 3) are able to move relative to one another in the direction x between an apart position of use in which the fifth and sixth panels (4, 5) are in their unfolded position and a together storage position in which the fifth and sixth panels (4, 5) are in their folded position, in which the sixth panel is made from a rigid material and includes a central portion and two side portions (17b, 17c) that are disposed on respective opposite sides of the central portion in the direction x, one of the side portions (17b, 17c) being mounted on and articulated to the first panel about a geometrical axis perpendicular to the direction x and the other of the side portions being mounted on and articulated to the second panel about a geometrical axis perpendicular to the direction x, each of said side portions (17b, 17c) being mobile in rotation relative to the central portion about a geometrical axis perpendicular to the direction x, the folding piece of luggage further including a holding device that is fixed to the central portion of the sixth panel, the folding piece of luggage including at least two castor mechanisms that are respectively fixed to the first and second panels (2, 3) on respective opposite sides of the third panel. - parallel first and second rigid panels (2, 3); - third and fourth rigid panels (6, 7), each of which is mounted on and articulated to one of the first and second panels (2, 3) between a deployed position in which said third or fourth panel (6, 7) extends between said first and second panels (2, 3), perpendicularly to said first and second panels (2, 3), and a retracted position in which said third or fourth panel (6, 7) extends parallel to said first and second panels (2, 3); the third and fourth panels (6, 7) defining with the first and second panels (2, 3) a rigid frame when the third and fourth panels (6, 7) are in their deployed position; - fifth and sixth panels (4, 5) each of which connects the first and second panels (2, 3) and that define with the first, second, third and fourth panels (2, 3, 6, 7), when the third and fourth panels (6, 7) are in their deployed position, an internal storage space of parallelepipedal shape; the fifth and sixth panels (4, 5) being deformable in a direction x perpendicular to said first and second panels (2, 3) between an unfolded position and a folded position so that, when the third and fourth panels (6, 7) are in their retracted position, the first and second panels (2, 3) are able to move relative to one another in the direction x between an apart position of use in which the fifth and sixth panels (4, 5) are in their unfolded position and a together storage position in which the fifth and sixth panels (4, 5) are in their folded position,