This graduation thesis shows the process of designing tractor powered flail mower with collector. Device must be pulled by a tractor and driven by PTO shaft and tractor hydraulics. The introduction gives an overview of the existing versions of tractor attachments for mowing grass and then gives a description of how to connect the device to the tractor and how to drive them. After that, an analysis of the current situation on the market of tractor mowers with a collection function was performed. After the market analysis, a functional decomposition and morphological matrix were made. Based on the solutions from the morphological matrix, two concepts were generated. Concept were evaluated and better one was selected and fully elaborated. For the selected concept, a calculation of non-standard parts, weld calculation and selection of standard components was made. A 3D model was created with required technical documentation .