The invention relates to a coaxial microwave applicator (1) for plasma production, comprising a coaxial tube formed by a central core (11) and an outer conductor (12) separated from the central core by an annular space (13) allowing propagation of microwaves. The applicator comprises: a cylindrical permanent magnet (21) disposed at the end of the central core (11); and at least one annular permanent magnet (22) disposed at the end of the outer conductor (12), all of the magnets (21, 22) disposed at the end of the coaxial tube (11, 12) having the same direction of magnetisation. The magnetisation of the magnets (21, 22) forms a magnetic field suitable for generating, in a zone (Z
RCE ) away from the end of the applicator, an electronic cyclotronic resonance coupling with the electric microwave field of the applicator (1). The external radius and the magnetisation of the annular magnet are selected such that the magnetic field lines (L) generated by the magnets pass through the coupling zone in a direction substantially parallel to the axis (X) of the applicator (1).