An engine system to be provided to a vehicle having an accelerator pedal, comprising: a supercharger driven by a crankshaft of an engine; an electromagnetic clutch disconnectably connecting the crankshaft to the supercharger; and a processor configured to: determine, based on a target engine torque and an engine speed, whether an operation range (A10, A11) of the engine is either one of a first range where the electromagnetic clutch is disengaged and a second range where the electromagnetic clutch is engaged; and control the engagement and/or disengagement of the electromagnetic clutch based on the determination of the processor, and an opening of the accelerator pedal, wherein when the operation range (A10, A11) of the engine shifts from the second range to the first range after the opening of the accelerator pedal increases at an increase rate below a given reference increase rate, the processor is configured to switch the electromagnetic clutch from the engaged state to the disengaged state after a given basic stand-by period passes from the shift to the first range, and wherein when the operation range (A10, A11) of the engine shifts from the second range to the first range after the opening of the accelerator pedal increases at an increase rate at or above the reference increase rate, the processor is configured to switch the electromagnetic clutch from the engaged state to the disengaged state after a given acceleration stand-by period passes from the shift to the first range, the acceleration stand-by period being longer than the basic stand-by period by a given added period. a supercharger driven by a crankshaft of an engine; an electromagnetic clutch disconnectably connecting the crankshaft to the supercharger; and a processor configured to: determine, based on a target engine torque and an engine speed, whether an operation range (A10, A11) of the engine is either one of a first range where the electromagnetic clutch is disengaged and a second range where the electromagnetic clutch is engaged; and control the engagement and/or disengagement of the electromagnetic clutch based on the determination of the processor, and an opening of the accelerator pedal, determine, based on a target engine torque and an engine speed, whether an operation range (A10, A11) of the engine is either one of a first range where the electromagnetic clutch is disengaged and a second range where the electromagnetic clutch is engaged; and control the engagement and/or disengagement of the electromagnetic clutch based on the determination of the processor, and an opening of the accelerator pedal, wherein when the operation range (A10, A11) of the engine shifts from the second range to the first range after the opening of the accelerator pedal increases at an increase rate below a given reference increase rate, the processor is configured to switch the electromagnetic clutch from the engaged state to the disengaged state after a given basic stand-by period passes from the shift to the first range, and wherein when the operation range (A10, A11) of the engine shifts from the second range to the first range after the opening of the accelerator pedal increases at an increase rate at or above the reference increase rate, the processor is configured to switch the electromagnetic clutch from the engaged state to the disengaged state after a given acceleration stand-by period passes from the shift to the first range, the acceleration stand-by period being longer than the basic stand-by period by a given added period.