A plasma generator is provided which includes: a microwave generation portion which generates a microwave; a wave guide for propagating the microwave; a plurality of plasma generation nozzles which are attached to the wave guide so as to be apart from each other in the direction where the microwave is propagated, receive the microwave, and generate and emit a plasmatic gas based on the energy of this microwave; and a plurality of stabs which correspond to a part or the whole part of the plasma generation nozzles and are each disposed in the wave guide so as to lie in a rear position a predetermined distance apart from each other in the direction where the microwave is propagated.