To provide a plasma source, in which light weight by thinning of a metal constituting the electrodes and which improved of assemblability and maintenability by reduction of the number of components, and simplifying of a cooling mechanism by gas cooling is realized.

The plasma source comprises a gas passage 30 for sending a prescribed gas to a treating material and a pair of electrodes 31, 32 which generate a gas discharge in the gas passage 30 under atmospheric pressure or in the pressure near-by it and generates an excitation active species of the gas; and the main surfaces 4a of a pair of plate shape dielectrics 4, in which a recessed groove 40 is cut and formed from one edge of the main surface 4a toward the other edge and a recessed cavity part 41 is cut and formed on the back face 4b; thin-film electrodes 31, 32 are arranged in the recessed cavity part 41, are arranged in close contact; and by the pair of the recessed grooves 40, the gas passage 30 is constructed, and furthermore the recessed cavity part 41 is formed in the cooling space of the electrodes 31, 32.