In a powertrain system including a first torque device and a second torque device having a larger response delay, a control device is configured to act as: a manipulated variable determination section that solves a linear programming problem to determine and output manipulated variables that maximally achieve target state quantities within a plurality of constraints; and a torque device control section. The plurality of constraints include, as upper and lower limit constraint values of the second manipulated variable, a maximum value and a minimum value of the second manipulated variable attainable at the next time step. The control device is further configured to act as a manipulated variable upper and lower limit calculation section that calculates, as the upper and lower limit constraint values, the above-described maximum value and the minimum value, based on the current rotational speed and estimated manipulated variable of the second torque device.