A cooling system and a cooling device are provided. The cooling device includes a container, a heat dissipation module, and a cooling module. The cooling module includes a cover plate and a heat dissipation fin assembly. The cover plate covers an opening of the container. The cover plate includes a cooling channel. The cooling channel is arranged in the cover plate and includes an inlet and an outlet. The inlet and the outlet are respectively located at two sides of the cover plate. One side of the heat dissipation fin assembly is in contact with a surface of the cover plate, and an other side of the heat dissipation fin assembly is located in the container. Through the above structure, a usage amount of heat transfer fluid injected into the container of the cooling device is lower than that of a conventional immersion cooling device.