A liquid cooling device for cooling a memory module is provided. The liquid cooling device includes a slot, installed on a motherboard, where the memory module is inserted into the slot; a first heat sink and a second heat sink, where the first, second heat sinks dissipate heat from the memory module between the first heat sink and the second heat sink, with the first, second heat sinks abutting the memory module; a liquid cooling plate, movably installed on a side of the slot, covering a top part of the memory module after the memory module is inserted into the slot, for liquid cooling of the first heat sink and the second heat sink; and at least one first fixing clamp, abutting surfaces of the first, second heat sinks, and clamping the first, second heat sinks and the memory module together.