A microwave plasma processing apparatus includes a processing space; a microwave generator which generates microwaves for generating a plasma; a distributor which distributes the microwaves to a plurality of waveguides; an antenna installed in a processing container to seal the processing space and to radiate microwaves distributed by the distributor, to the processing space; and a monitor unit configured to monitor a voltage of each of the plurality of waveguides. A control unit acquires a control value of a distribution ratio of the distributor, which corresponds to a difference between a voltage monitor value of the monitor unit and a predetermined voltage reference value, from a storage unit that stores the difference and the control value corresponding to each other. The control unit is also configured to control the distribution ratio of the distributor, based on the acquired control value.