NOVELTY - The fuel-using system includes a current sensor (8) that detects the flow rate of the fuel gas relating to the use of a fuel-using equipment in the form of a fuel cell stack (1). A pressure sensor (9) detects the pressure of the fuel gas on the upstream side of a pressure reducing valve (5). A control device (7) sequentially sets the electromagnetic force of the solenoid (6) of an electromagnetic shutoff valve (10) for opening the shutoff valve at appropriate amount to supply use flow gas rate to the fuel-using equipment based on detection values of the current sensor and pressure sensor.    USE - Fuel-using system used as fuel cell system in a vehicle. Can also be used as e.g. internal combustion engine system using hydrogen gas as fuel.    ADVANTAGE - Provides a fuel-using system which has a function of cutting off fuel gas supply from a fuel supply source. Ensures reduced time period from the time when a fuel gas leak occurs in a gas supply path to the time when a shutoff valve is actually closed. Ensures that the electromagnetic force of the shutoff valve to the gas supply path can be always appropriately and easily set. Prevents malfunction of the shutoff valve in a situation in which no leak occurs in the gas supply path. Ensures that the shutoff valve can be rapidly closed at the occurrence of fuel gas leak, even when it is used under difficult circumstances in which signal noise is caused often from auxiliary equipments such as pumps and valves.    DETAILED DESCRIPTION - The electromagnetic shutoff valve is provided in a fuel supply source in the form of a hydrogen tank (2), or a part adjacent to the fuel supply source of the gas supply path (3). The fuel supply source provides fuel gas to the fuel-using equipment. The gas supply path connects the fuel supply source to the fuel-using equipment. The shutoff valve is opened by the electromagnetic force of the solenoid with energization of a valve body in the valve-closing direction by an energizing unit. The pressure reducing valve is provided at the downstream side of the shutoff valve to reduce pressure of the fuel gas passing through the shutoff valve from the fuel supply source.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic diagram showing the configuration of the fuel-using system.    Fuel cell stack (1)    Hydrogen tank (2)    Gas supply path (3)    Pressure reducing valve (5)    Solenoid (6)    Control device (7)    Current sensor (8)    Pressure sensor (9)    Electromagnetic shutoff valve (10)