An immersion cooling system miniaturized by the omission of a pump and heat exchanger includes a first casing for containing a non-conductive coolant in which a heat-generating component is immersed, fins disposed on and located outside the first casing, and a second casing. The first casing is disposed in the second casing, and the second casing defines a first vent hole exposing the fins. The immersion cooling system dissipates heat by means of natural convection.