<p>A microwave processing device includes: a periodic structure body which forms a surface-wave transmission line to transmit surface waves of microwaves; an oscillator which generates microwave power; and a transmitting part which transmits the microwave power generated by the oscillator to the periodic structure body, wherein a matching part is provided at a connecting portion between the periodic structure body and the transmitting part, and an impedance of the matching part is set to a value between an impedance of the periodic structure body and an impedance of the transmitting part.</p>
