A parallel plate ECR plasma processing system is able to extend a plasma density region capable of keeping a continuous, uniform state. In this system, a first magnetic field-forming means formed of a solenoid coil and a second magnetic field-forming means are provided so that a the distribution of a direction of a magnetic line of flux on the surface of a planar plate is controlled by a combined magnetic field from the first and second magnetic field-forming means thereby controlling the distribution in degree of the interactions of the magnetic field and an electromagnetic wave. This control ensures the uniformity of a plasma under high density plasma formation conditions, thus enabling one to form a continuous plasma over a wide range of low to high densities. Thus, there can be realized a plasma processing system that ensures processing under wide plasma conditions including high-speed processing under high density conditions.