A microwave plasma generator, which functions under high pressure, has been developed and used in the fabrication of fine carbon particles. The plasma generator is a two-stage-type resonator, which consists of rectangular and semi-cylindrical-type resonators which are coupled in series for torching plasma and keeping it stable under high pressure. The plasma can be torched in helium gas at 3 × 106 Pa by tuning the dimensions of apparatus elements. Fine carbon particles of ~50 nm are obtained using a mixture of helium and methane gas. The particles are found to be crystalline from the results of transparent electron microscopy and diffraction analysis.