The invention relates to a dewatering apparatus of a fiber web machine including a frame construction (13) greater in its length than width. The frame construction (13) has intermediate supports (14) fastened thereto at an interval of each other which are set in the cross direction relative to the longitudinal direction of the frame construction (13). The dewatering apparatus also includes at least one foil blade support (15), longitudinal relative to the frame construction (13), which is supported to openings (16) arranged in the intermediate supports (14). The opening (16) includes a bottom (30). In addition, the foil blade support (15) is set at a desired distance from the bottom (30) of the opening (16) in each intermediate support (14), and there is a weld connection (18) between the foil blade support (15) and the intermediate support (14). The invention also relates to a method for manufacturing a dewatering apparatus of a fiber web machine.