PURPOSE: To provide a surface-treating apparatus in which a material to be treated is not damaged by a line of magnetic force when a processing speed is improved by the line of magnetic force.

CONSTITUTION: The surface-treating apparatus comprises an exciting chamber 3 in which reactive gas to be excited by a microwave is introduced, a magnet 37 disposed on the outer periphery of the chamber to generate a line H of magnetic force in the chamber, a treating chamber 21 in which a material 24 to be treated on the surface by reactive gas excited by the exciting chamber in communication with the exciting chamber is installed, and a ventilation element 28 made of a magnetic material for preventing leakage of the line H of magnetic force generated by the magnet 37 to be provided between the treating chamber and the exciting chamber and coated with a corrosion resistant film on the surface.