A fuel supply control device for a fuel supply device (F, F 1), the fuel supply device (F, F 1) being a device which supplies a fuel supplied from a fuel tank to a gas turbine and including a low-pressure pump, a high-pressure pump, an electric motor, a thermometer, a pump differential pressure meter, a pressurizing valve, an orifice, a valve differential pressure meter, and the fuel supply control device, wherein the fuel supply control device is configured to use a parallel flow path of the orifice and the pressurizing valve as a complex pressurizing valve for a fuel supply amount and control the high-pressure pump on the basis of a differential pressure (ΔP) before and after the complex pressurizing valve detected by the valve differential pressure meter, the fuel supply control device is configured to control the high-pressure pump on the basis of a first fuel measurement amount obtained from the differential pressure (ΔP) before and after the complex pressurizing valve and a mutual relationship between the differential pressure (ΔP) before and after the complex pressurizing valve and a fuel flow rate when a rotational speed of the high-pressure pump is below a predetermined threshold value, and the fuel supply control device is configured to control the high-pressure pump on the basis of a second fuel measurement amount obtained from a pump volume efficiency (ηv) in consideration of an internal leak area (A leak) of the high-pressure pump and a theoretical pump discharge volume (Vth) when the rotational speed exceeds the predetermined threshold value, characterized in that the fuel supply control device comprises: a flow rate calculation unit which calculates the first fuel measurement amount and the second fuel measurement amount; a switching logic circuit which generates a switching signal by comparing the rotational speed of the high-pressure pump with the predetermined threshold value; a flow rate selection switch which selectively selects the first fuel measurement amount or the second fuel measurement amount on the basis of the switching signal; a subtractor which calculates a deviation between an output of the flow rate selection switch and a control target value; and a control calculation unit which generates an operation amount of the high-pressure pump by performing a predetermined control calculation process on the deviation. wherein the fuel supply control device is configured to use a parallel flow path of the orifice and the pressurizing valve as a complex pressurizing valve for a fuel supply amount and control the high-pressure pump on the basis of a differential pressure (ΔP) before and after the complex pressurizing valve detected by the valve differential pressure meter, the fuel supply control device is configured to control the high-pressure pump on the basis of a first fuel measurement amount obtained from the differential pressure (ΔP) before and after the complex pressurizing valve and a mutual relationship between the differential pressure (ΔP) before and after the complex pressurizing valve and a fuel flow rate when a rotational speed of the high-pressure pump is below a predetermined threshold value, and the fuel supply control device is configured to control the high-pressure pump on the basis of a second fuel measurement amount obtained from a pump volume efficiency (ηv) in consideration of an internal leak area (A leak) of the high-pressure pump and a theoretical pump discharge volume (Vth) when the rotational speed exceeds the predetermined threshold value, characterized in that the fuel supply control device comprises: a flow rate calculation unit which calculates the first fuel measurement amount and the second fuel measurement amount; a switching logic circuit which generates a switching signal by comparing the rotational speed of the high-pressure pump with the predetermined threshold value; a flow rate selection switch which selectively selects the first fuel measurement amount or the second fuel measurement amount on the basis of the switching signal; a subtractor which calculates a deviation between an output of the flow rate selection switch and a control target value; and a control calculation unit which generates an operation amount of the high-pressure pump by performing a predetermined control calculation process on the deviation. a flow rate calculation unit which calculates the first fuel measurement amount and the second fuel measurement amount; a switching logic circuit which generates a switching signal by comparing the rotational speed of the high-pressure pump with the predetermined threshold value; a flow rate selection switch which selectively selects the first fuel measurement amount or the second fuel measurement amount on the basis of the switching signal; a subtractor which calculates a deviation between an output of the flow rate selection switch and a control target value; and a control calculation unit which generates an operation amount of the high-pressure pump by performing a predetermined control calculation process on the deviation.