To provide a bonnet for plural kinds of tractors having the different lengths at low cost.

This structure of a bonnet 10 is provided on a tractor having a structure in which an engine 26 is mounted on a machine body front part and a fuel tank 21 is provided behind the engine, covers the upper parts of the engine 26 and the fuel tank 21, and can be freely opened and closed around a hinge pin supported on a frame part 20 for supporting the fuel tank 21. A main bonnet part 51 for covering the engine and a sub bonnet part 52 extending rearward from the rear end of the main bonnet part 51 and for covering the fuel tank 21 are connected to each other, a hinge arm 32 is attached to the rear end of the sub bonnet part 25, the main bonnet 51 is shared, a plurality of sub bonnet parts 25 having the different lengths are prepared and connected to the rear end of the main bonnet 51, and therefore, the bonnets having the different lengths can be constituted at low cost.