A pressurized fluidized bed combined electricity generation system for improving gas turbine output increases and prevention of surging is provided. This pressurized fluidized bed combined electricity generation system is a combined electricity generation system including a steam turbine; a pressurized fluidized bed boiler for generating steam for supply to the steam turbine by combusting air from an air supply system and fuel from a fuel supply system; a gas turbine driven by exhaust gas such as combustion gas from the pressurized fluidized bed boiler and air; and a compressor directly coupled to the gas turbine. In addition, this pressurized fluidized bed combined electricity generation system has a first bypass duct communicating between the outlet side of the compressor and the exhaust gas side of the gas turbine and having a switching valve; a second bypass duct communicating between the outlet side of the compressor and the inlet side of the gas turbine and having a switching valve; and a control device which receives measured pressure values of a pressure detector which measures the pressure at the outlet of the compressor. This control device controls the switching valves of the first and second bypass ducts based on the relationship between the degree of opening of the inlet variable guide vane of the compressor which is determined in advance and a surge limiting pressure. A part of the steam generated by the pressurized fluidized bed boiler is extracted, mixed in with the exhaust gas or the above-mentioned air, and supplied to the gas turbine. Air from the compressor is supplied as fuel for the pressurized fluidized bed boiler.