PURPOSE: To nuclear fuse deuteron and/or or triton at low temperature and peacefully utilize the generated energy by bringing hydrogen and nucleus to be nuclear fused into contact with a microcluster.

CONSTITUTION: A microcluster to be used contains 30,000-100,000 atoms, preferably, up to 1000 atoms, and these atoms belong to at least the subgenus of the periodic table, and cooled by a carrier medium, whereby finely distributed particle can be provided at high temperature. This microcluster 3 is adhered onto a substrate layer 4, and the space with a counter electrode 12 is supported by an insulating particle 19 to form a gas chamber 16. The substrate layer 4, a substrate base 15 for supporting it, and the counter electrode 12 are also formed as porous hollowed cylinders, and a gas to be nuclear fused is axially advanced in an air conditioner 17, and radially passed through the base 15, the substrate 4, the gas chamber 16, and the counter electrode 12. The counter electrode 12 is used as a waste heat body 18 since the heat generated in the gas chamber 16 is utilized, and a work can be progressed at a using temperature higher than the nuclear fusion temperature.