Inner partitions disposed within a cooling tank have an open space to form arrayed housing parts, and at least one unit of electronic device housed in each of the housing parts. A lifting mechanism includes a tower having a guide and a driving source for raising and lowering an arm, a slide mechanism attached to the cooling tank, and a stopper for restricting the tower's movement so that a range of the tower's motion in a width direction of the cooling tank does not exceed at least a width of the open space. The slide mechanism supports the tower movably with respect to the cooling tank in a horizontal plane located above the open space. The liquid immersion cooling system can safely lift or lower the electronic devices densely housed within the cooling tank without requiring the stage in the periphery of the installation surface of the cooling tank.