A throttle device comprising: a plurality of throttle units (11, 12) providable in an engine for each of cylinders or for each of cylinder groups, each of the throttle units including a throttle body having intake air passages (13a, 13b, 13c, 13d) corresponding to the plurality of cylinders (2a, 2b, 2c, 2d) of the engine, a throttle shaft rotatably supported by the throttle body, throttle valves (16a, 16b, 16c, 16d) secured to the throttle shaft to open and close the intake air passages (13a, 13b, 13c, 13d) for the cylinders (2a, 2b, 2c, 2d), and a motor (17a, 17b) driving and rotating the throttle shaft, wherein a first motor that is the motor provided in a first throttle unit and a second motor that is the motor provided in a second throttle unit out of the plurality of throttle units (11, 12) have mutually different responsivities to a change in rotation speed, wherein the first motor and the second motor are electric motors, and at least either numbers of windings or wire diameters of coils are set to be different between the first motor and the second motor, wherein the throttle device further comprises: a cylinder deactivation control unit stopping operations only of the second motor out of the first motor and the second motor and setting the throttle valves (16c, 16d) of the second throttle unit to have a predetermined degree of opening in a predetermined operating region of the engine, and deactivating combustion of the cylinder or the cylinder group (2c, 2d) corresponding to the second throttle unit, wherein the responsivity to a change in rotation speed of the second motor is higher than the responsivity to a change in rotation speed of the first motor. a plurality of throttle units (11, 12) providable in an engine for each of cylinders or for each of cylinder groups, each of the throttle units including a throttle body having intake air passages (13a, 13b, 13c, 13d) corresponding to the plurality of cylinders (2a, 2b, 2c, 2d) of the engine, a throttle shaft rotatably supported by the throttle body, throttle valves (16a, 16b, 16c, 16d) secured to the throttle shaft to open and close the intake air passages (13a, 13b, 13c, 13d) for the cylinders (2a, 2b, 2c, 2d), and a motor (17a, 17b) driving and rotating the throttle shaft, wherein a first motor that is the motor provided in a first throttle unit and a second motor that is the motor provided in a second throttle unit out of the plurality of throttle units (11, 12) have mutually different responsivities to a change in rotation speed, wherein the first motor and the second motor are electric motors, and at least either numbers of windings or wire diameters of coils are set to be different between the first motor and the second motor, wherein the throttle device further comprises: a cylinder deactivation control unit stopping operations only of the second motor out of the first motor and the second motor and setting the throttle valves (16c, 16d) of the second throttle unit to have a predetermined degree of opening in a predetermined operating region of the engine, and deactivating combustion of the cylinder or the cylinder group (2c, 2d) corresponding to the second throttle unit, wherein the responsivity to a change in rotation speed of the second motor is higher than the responsivity to a change in rotation speed of the first motor. a cylinder deactivation control unit stopping operations only of the second motor out of the first motor and the second motor and setting the throttle valves (16c, 16d) of the second throttle unit to have a predetermined degree of opening in a predetermined operating region of the engine, and deactivating combustion of the cylinder or the cylinder group (2c, 2d) corresponding to the second throttle unit, wherein the responsivity to a change in rotation speed of the second motor is higher than the responsivity to a change in rotation speed of the first motor.