A liquid cooled heat dissipation device including a housing, at least two cooling fin modules, an input pipe, and an output pipe is provided. The housing has an accommodation space. The at least two cooling fin modules are disposed in the accommodation space. The input pipe is disposed on the top plate, the front plate, the rear plate, or one of the side plates of the housing and communicates with the accommodation space. The output pipe is disposed on the top plate, the front plate, the rear plate, or the other one of the side plates of the housing and communicates with the accommodation space. The at least two cooling fin modules have different arrangement densities and different fin thicknesses.