PURPOSE: To utilize the whole length of a trailer for space for heavy machines by forming a connection member integrally to be forward/back rotatably connected to a car body at an axial position between a first axle and a second axle.

CONSTITUTION: A trailer has axles 1, 2, 3 as a first to a third axles provided along width of a car body, and an irregularly formed walking boom 4 as a connection member to connect these axles to each other. The axle 1 is provided at a center part of the width at a rear part of the car body, and the axles 2, 3 are provided at symmetric positions in the width from a center C of the width on the back of the axle 1. Shaft parts 4-1, 4-2, 4-3 to be inserted into boss parts of the exles 1, 2, 3 are provided to be forward/back rotatably connected to the car body at an axial direction position between the axle 1 and the axle 2. When length Y of a crawler part 100a of a heavy machine 100 is similar to length L of each side part 13a of a loading part 13, the heavy machine can be loaded.