Abstract: The plasma torch has a cathode supporter having a front end and a rear end, mounted on the body at the rear end thereof; a button-cathode for generating plasma arc, which is assembled to the front end of the cathode supporter; a hollow-cathode having an inner surface and an outer surface, surrounding the button-cathode, the inner surface of which is spaced from the button-cathode, being assembled to the cathode supporter, and being made of material with higher work function than material for the button-cathode. The plasma gas flows along the outer surface to accomplish low gas pressure between the inner surface of the hollow-cathode and the button-cathode. A multiple-solenoid coil is adapted to rotate arc root around the button-cathode and to move arc root axially along the surface of the button-cathode.