The embodiment of the invention provides a power supply device and a power supply system, and relates to the technical field of battery thermal management. The power supply device comprises a liquid-cooling plate, heat dissipation plates and a battery module, wherein the liquid-cooling plate comprises a passage, the passage is used for a liquid to pass through and penetrates through a first side surface and a second side surface, which are opposite to each other, of the liquid-cooling plate, the heat dissipation plates are arranged on a third side surface of the liquid-cooling plate at equal intervals, the battery module comprises a plurality of single batteries, each single battery is arranged among the heat dissipation plates arranged at equal intervals, and heat of the single batteries is dissipated by the heat dissipation plates and the liquid-cooling plate. The power supply device and the power supply system can be used for rapidly dissipating heat of the battery module, so that the battery module works in a relatively excellent charge-discharge state, the service lifetime of the battery is further prolonged, the performance of the battery is further improved, and electric energy output stability, safety and reliability of the battery are ensured.