A control device which controls a fuel gas supply system which includes a compressor which compresses fuel gas and supplies the compressed fuel gas to a load apparatus, inflow amount regulating means for regulating an amount of fuel gas which flows into the compressor, and an anti-surge valve for returning the fuel gas discharged from the compressor to an inlet side of the compressor, wherein the control device comprises: a main pressure control unit which controls the inflow amount regulating means and the anti-surge valve on the basis of a feedforward control value which is generated on the basis of a load of the load apparatus and a predetermined conversion process, and a feedback control value which is generated on the basis of a deviation between a set value of a discharge pressure of the compressor and a measured value of the discharge pressure of the compressor; and an emergency pressure control unit which calculates a bias-added control value (MV3') by adding a predefined bias value (BIAS) to an anti-surge valve control value which is calculated on the basis of at least one of the feedforward control value and the feedback control value and controls the anti-surge valve, and switches the anti-surge valve control value to the bias-added control value (MV3') on the basis of occurrence of load variation of a predetermined value or more to control the anti-surge valve, and whereby the emergency pressure control unit sets the bias-added control value (MV3') to the predefined bias value (BIAS) when the feedforward control value is a value of a closed state of the anti-surge valve, and controls such that the bias-added control value (MV3') becomes a smaller value as the feedforward control value becomes larger when the feedforward control value is a value of an open state of the anti-surge valve. a main pressure control unit which controls the inflow amount regulating means and the anti-surge valve on the basis of a feedforward control value which is generated on the basis of a load of the load apparatus and a predetermined conversion process, and a feedback control value which is generated on the basis of a deviation between a set value of a discharge pressure of the compressor and a measured value of the discharge pressure of the compressor; and an emergency pressure control unit which calculates a bias-added control value (MV3') by adding a predefined bias value (BIAS) to an anti-surge valve control value which is calculated on the basis of at least one of the feedforward control value and the feedback control value and controls the anti-surge valve, and switches the anti-surge valve control value to the bias-added control value (MV3') on the basis of occurrence of load variation of a predetermined value or more to control the anti-surge valve, and whereby the emergency pressure control unit sets the bias-added control value (MV3') to the predefined bias value (BIAS) when the feedforward control value is a value of a closed state of the anti-surge valve, and controls such that the bias-added control value (MV3') becomes a smaller value as the feedforward control value becomes larger when the feedforward control value is a value of an open state of the anti-surge valve.