A target torque control device and a target torque control method capable of maintaining a temperature within an allowable temperature even when a lock-up clutch is engaged are provided. In a target torque control device (ECU) for setting a target torque of a prime mover (E) that outputs a torque to a multi-stage transmission (3) including a torque converter (2) and a lock-up clutch (2a), when the lock-up clutch (2a) is in an engaged state (STEP 1), a target torque reduction control for reducing a target torque of the prime mover (E) (STEP 3) is executed so that an output torque of the prime mover (E) becomes an output torque at which a heat generation temperature of the lock-up clutch (2a) does not exceed an allowable temperature during the up-shift transmission (STEP 2).