A cooling device includes a cooling unit (10) penetrated by a fluid to be cooled, in particular hydraulic oil, and a filter unit (12) for filtering the fluid. The filter unit (12) extends along a longitudinal side of the cooling unit (10). A fluid collecting space (16) is arranged between the filter unit (12) and the cooling unit (10). The fluid collecting space (16) has a uniform flow cross-section and is at least partially closed against the filter unit (12) by a concavely curved limitating wall (36). The optimized fluid guidance obtained results in a uniformization of speed, while at the same time avoiding cavities and turbulences to ensure a trouble-free and energetically favorable operation of the cooling device.