To improve pillar rigidity and handling performance of piping in a pillar cover in a cabin of a working vehicle such as a tractor by bendwise forming a fixed surface into a stepped shape, and storing piping of air conditioner or electric wiring in a space defined in a piller by the cover.

A cabin of a tracter is supported in its ceiling on which an air conditioner body and/or the like is mounted by pillers erected at forward and rearward parts and pillers 14 erected on both sides of the cabin. In this case, the side piller 14 is constructed of a substantially U shape section piller frame 18 opened toward the inside of the cabin 3 and a cover 19 covering the opening side. The cover 19 is formed out of a fixed face 21 having steps of bendwise stepped shape in the forward and rearward direction and a cover face 22. In a space between the frame 18 and the cover 19, a valve assembly 23, hot water hose 24 and pipes 26, 27 for harness to be used for an air conditioner are provided.