To solve the problem that a stand rod supporting an open attitude of a bonnet of a work vehicle such as a tractor in the tensed state touches an arm or a shoulder of an operator working for inspection or maintenance in the bonnet, which deteriorates workability.

A opening/closing part S of the bonnet 6 is constituted by a support tool 21 provided on the side of a traveling machine body 4 and a mounting tool 22 provided on the side of a rotation base end of the bonnet 6, the mounting tool 22 is mounted smoothly and rotatably so as to open/close the bonnet 6 for a rotation fulcrum 25 provided at the support tool 21, and an attitude holding part K for holding the open attitude state of the bonnet 6 is formed between the support tool 21 and the mounting tool 22.