Frame structure for working vehicle

b bRigidity of a frame of a working vehicle is improved by a simple structure and production costs are reduced by reducing the number of parts of a working vehicle. Pipes are provided on both left and right sides at the center in the front-rear direction of a side frame , and each pipe has a rectangular cross-section and penetrates an intermediate partition in the front-rear direction from a mast section up to a transmission section. Tie-down holes are formed in a front face plate to which the front end of a frame is connected, and a plate connected to a side frame is provided at the bottom surface of each mast section protruding outward from the side frame . Tanks installed on the working vehicle are suspended from the plate bodies , and a lift arm installation boss provided at each mast section is supported at both ends. A U-shaped reinforcement member connects the upper surface of mast partition plate of a mast section and left and right bosses.