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 apparatus driven by the engine; a power transmission device including an input shaft, an output shaft, a gear mechanism, an energy-generating motor, a first clutch, and a locking means, the power transmission device being configured to transmit the drive power from the engine to the travel apparatus; a controller configured to control the power transmission device; and an energy storage unit configured to store the energy generated by the energy-generating motor, the power transmission device being configured such that changing the speed of the energy-generating motor changes the speed ratio of the output shaft relative to the input shaft in the power transmission device; the gear mechanism including a planetary gear mechanism, the gear mechanism being configured to transmit the rotations of the input shaft to the output shaft; the planetary gear mechanism including a first rotation element, a second rotation element, and a third rotation element which are mutually different; the first clutch being provided along the power transmission route between the engine and the first rotation element; the locking means being configured to lock or release the second rotation element; the energy-generating motor being connected to the third rotation element; the controller including a speed adjustment unit configured to adjust the speed of two rotation shafts in the first clutch; and characterized in that the controller is configured to lock the second rotation element using the locking means, converge the speeds of the two rotation shafts in the first clutch using the speed adjustment unit to cause the first clutch to engage, and cause the energy-generating motor to rotate using the drive power from the engine to thereby accumulate energy in the energy storage unit. an engine; a hydraulic pump driven by the engine; a work implement driven by hydraulic fluid discharged from the hydraulic pump; a travel apparatus driven by the engine; a power transmission device including an input shaft, an output shaft, a gear mechanism, an energy-generating motor, a first clutch, and a locking means, the power transmission device being configured to transmit the drive power from the engine to the travel apparatus; a controller configured to control the power transmission device; and an energy storage unit configured to store the energy generated by the energy-generating motor, the power transmission device being configured such that changing the speed of the energy-generating motor changes the speed ratio of the output shaft relative to the input shaft in the power transmission device; the gear mechanism including a planetary gear mechanism, the gear mechanism being configured to transmit the rotations of the input shaft to the output shaft; the planetary gear mechanism including a first rotation element, a second rotation element, and a third rotation element which are mutually different; the first clutch being provided along the power transmission route between the engine and the first rotation element; the locking means being configured to lock or release the second rotation element; the energy-generating motor being connected to the third rotation element; the controller including a speed adjustment unit configured to adjust the speed of two rotation shafts in the first clutch; and characterized in that the controller is configured to lock the second rotation element using the locking means, converge the speeds of the two rotation shafts in the first clutch using the speed adjustment unit to cause the first clutch to engage, and cause the energy-generating motor to rotate using the drive power from the engine to thereby accumulate energy in the energy storage unit. lock the second rotation element using the locking means, converge the speeds of the two rotation shafts in the first clutch using the speed adjustment unit to cause the first clutch to engage, and cause the energy-generating motor to rotate using the drive power from the engine to thereby accumulate energy in the energy storage unit.