A throttle device comprising: a plurality of throttle units (11, 12) providable in an engine for each of cylinders (2a, 2b, 2c, 2d) or each of cylinder groups, each of the throttle units (11, 12) including a throttle body having intake air passages (13a, 13b, 13c, 13d) corresponding to the cylinders 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 for the cylinders, a motor driving and rotating the throttle shaft, and a biasing portion biasing the throttle shaft to cause the throttle valves (16a, 16b, 16c, 16d) to have a first predetermined degree of opening, wherein a biasing torque of the biasing portion provided in a first throttle unit and a biasing torque of the biasing portion provided in a second throttle unit out of the plurality of throttle units (11, 12) are different from each other at a same degree of opening of the throttle valves (16a, 16b, 16c, 16d), wherein the throttle device further comprises: a cylinder deactivation control unit stopping operations only of the motor of the second throttle unit out of the first throttle unit and the second throttle unit, in a predetermined operating region of the engine, setting the throttle valves (16c, 16d) of the second throttle unit to have a second predetermined degree of opening, and deactivating combustion of the cylinder or the cylinder group (2c, 2d) corresponding to the second throttle unit, wherein the biasing torque of the biasing portion of the second throttle unit is larger than the biasing torque of the biasing portion of the first throttle unit at the same degree of opening of the throttle valves (16a, 16b, 16c, 16d). a plurality of throttle units (11, 12) providable in an engine for each of cylinders (2a, 2b, 2c, 2d) or each of cylinder groups, each of the throttle units (11, 12) including a throttle body having intake air passages (13a, 13b, 13c, 13d) corresponding to the cylinders 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 for the cylinders, a motor driving and rotating the throttle shaft, and a biasing portion biasing the throttle shaft to cause the throttle valves (16a, 16b, 16c, 16d) to have a first predetermined degree of opening, wherein a biasing torque of the biasing portion provided in a first throttle unit and a biasing torque of the biasing portion provided in a second throttle unit out of the plurality of throttle units (11, 12) are different from each other at a same degree of opening of the throttle valves (16a, 16b, 16c, 16d), wherein the throttle device further comprises: a cylinder deactivation control unit stopping operations only of the motor of the second throttle unit out of the first throttle unit and the second throttle unit, in a predetermined operating region of the engine, setting the throttle valves (16c, 16d) of the second throttle unit to have a second predetermined degree of opening, and deactivating combustion of the cylinder or the cylinder group (2c, 2d) corresponding to the second throttle unit, wherein the biasing torque of the biasing portion of the second throttle unit is larger than the biasing torque of the biasing portion of the first throttle unit at the same degree of opening of the throttle valves (16a, 16b, 16c, 16d). a cylinder deactivation control unit stopping operations only of the motor of the second throttle unit out of the first throttle unit and the second throttle unit, in a predetermined operating region of the engine, setting the throttle valves (16c, 16d) of the second throttle unit to have a second predetermined degree of opening, and deactivating combustion of the cylinder or the cylinder group (2c, 2d) corresponding to the second throttle unit, wherein the biasing torque of the biasing portion of the second throttle unit is larger than the biasing torque of the biasing portion of the first throttle unit at the same degree of opening of the throttle valves (16a, 16b, 16c, 16d).