A work vehicle, comprising: an engine; a hydraulic pump driven by the engine; a work implement driven by hydraulic fluid discharged from the hydraulic pump; a travel device driven by the engine; a power-transmission device (24, 124) configured to transmit driving power from the engine to the travel device; and a control unit for controlling the power-transmission device (24, 124); wherein, the power-transmission device (24, 124) has: an input shaft; an output shaft; a gear mechanism for transmitting rotation of the input shaft to the output shaft, the gear mechanism including a plurality of planetary gear mechanisms and a mode-switching mechanism for selectively switching a drive-power transmission path in the power-transmission device (24, 124) among a plurality of modes; and a motor connected to a rotating element of the planetary gear mechanisms; and, the power-transmission device (24, 124) is configured so that a rotation speed ratio of the output shaft with respect to the input shaft is changed by changing a rotation speed of the motor, and the control unit has: a target-input-torque determination unit that determines a target input torque (Te_ref) which is a torque target value inputted to the power-transmission device (24, 124) via the input shaft; a target-output-torque determination unit that determines a target output torque (To_ref) which is a torque target value outputted from the power-transmission device (24, 124); a storage unit for storing torque balance information for defining a relationship between the target input torque (Te_ref) and the target output torque (To_ref) so as to achieve a balance of the torques of the power-transmission device (24, 124); and a command-torque determination unit that uses the torque balance information to determine a command torque for the motor from the target input torque (Te_ref) and the target output torque (To_ref). an engine; a hydraulic pump driven by the engine; a work implement driven by hydraulic fluid discharged from the hydraulic pump; a travel device driven by the engine; a power-transmission device (24, 124) configured to transmit driving power from the engine to the travel device; and a control unit for controlling the power-transmission device (24, 124); wherein, the power-transmission device (24, 124) has: an input shaft; an output shaft; a gear mechanism for transmitting rotation of the input shaft to the output shaft, the gear mechanism including a plurality of planetary gear mechanisms and a mode-switching mechanism for selectively switching a drive-power transmission path in the power-transmission device (24, 124) among a plurality of modes; and a motor connected to a rotating element of the planetary gear mechanisms; and, an input shaft; an output shaft; a gear mechanism for transmitting rotation of the input shaft to the output shaft, the gear mechanism including a plurality of planetary gear mechanisms and a mode-switching mechanism for selectively switching a drive-power transmission path in the power-transmission device (24, 124) among a plurality of modes; and a motor connected to a rotating element of the planetary gear mechanisms; and, the power-transmission device (24, 124) is configured so that a rotation speed ratio of the output shaft with respect to the input shaft is changed by changing a rotation speed of the motor, and the control unit has: a target-input-torque determination unit that determines a target input torque (Te_ref) which is a torque target value inputted to the power-transmission device (24, 124) via the input shaft; a target-output-torque determination unit that determines a target output torque (To_ref) which is a torque target value outputted from the power-transmission device (24, 124); a storage unit for storing torque balance information for defining a relationship between the target input torque (Te_ref) and the target output torque (To_ref) so as to achieve a balance of the torques of the power-transmission device (24, 124); and a command-torque determination unit that uses the torque balance information to determine a command torque for the motor from the target input torque (Te_ref) and the target output torque (To_ref). a target-input-torque determination unit that determines a target input torque (Te_ref) which is a torque target value inputted to the power-transmission device (24, 124) via the input shaft; a target-output-torque determination unit that determines a target output torque (To_ref) which is a torque target value outputted from the power-transmission device (24, 124); a storage unit for storing torque balance information for defining a relationship between the target input torque (Te_ref) and the target output torque (To_ref) so as to achieve a balance of the torques of the power-transmission device (24, 124); and a command-torque determination unit that uses the torque balance information to determine a command torque for the motor from the target input torque (Te_ref) and the target output torque (To_ref).