A truck-trailer for easy changeability and wider range of applicability in simplified construction to increase transportation capacity and improve changeability and applicability having the front and the rear sections of the main deck each pivoted with a retractable slope; the rear end of the main deck being disposed of a multi-sectional access slope for the access by different types of vehicles; and an elevation deck set being provided on the main deck to cope with the load of various types of vehicles to increase loading capacity.