There is provided a plasma processing apparatus enabling uniform plasma processing over the entire surface of a sample, without causing abnormal discharge even when the electromagnetic field strength is strong as in the case of the inductive coupling method. The plasma processing apparatus includes a process chamber, a first dielectric vacuum window, an inductive coil, a radio-frequency power supply, a gas supply unit, and a sample holder. The gas supply unit includes a second dielectric gas guide plate and a third dielectric island member. The second dielectric gas guide plate is located near below the vacuum window, and has a gas inlet port in the center. The third dielectric island member is provided in a gap between the vacuum window and the gas guide plate. The dielectric constant of the third dielectric is higher than the dielectric constant of the first and second dielectrics.