A method of controlling plasma includes providing a plasma processing apparatus that includes N microwave introducing radiators disposed in a circumferential direction of a ceiling plate of a processing container so as to introduce microwaves for generating plasma into the processing container, wherein N≥2; and M sensors and configured to monitor at least one of electron density Ne and electron temperature Te of the plasma generated in the processing container, wherein M equals to N or a multiple of N. The method further includes controlling at least one of a power and a phase of the microwaves introduced from the microwave introducing radiators based on at least one of electron density Ne and electron temperature Te of the plasma monitored by the M sensors.