Abstract: A nuclear fusion system includes: a muon generation unit for generating negative muons; a gas supply unit for circulating and supplying gaseous deuterium or gaseous deuterium-tritium mixture as raw material gas for a nuclear fusion reaction; and a Laval nozzle for accelerating the raw material gas to supersonic velocity including a flow regulation portion in which the muons are decelerated and a reaction portion in which the nuclear fusion reaction occurs, wherein an oblique shockwave, which is generated as a result of collision of a shock wave generator arranged inside the reaction portion and the raw material gas accelerated to supersonic velocity, converges on a center axis of the Laval nozzle, and thereby a high-density gas target is retained in a gas phase, and wherein the muons are introduced into the high-density gas target, and thereby the nuclear fusion reaction is caused to occur.