A plasma generating unit capable of improving in-surface uniformity of plasma and a plasma processing apparatus using the same are provided. The plasma generating unit provided in the plasma processing apparatus includes a dielectric window 16; a slot plate 20 provided on the dielectric window 16; and a coaxial waveguide electrically connected to the slot plate 20 and configured to transmit a microwave. The coaxial waveguide includes an inner conductor 31; and an outer conductor 32 configured to surround the inner conductor 31. The plasma generating unit further includes a pressing component PM configured to elastically press the inner conductor 31 toward the slot plate.