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; a power transmission device (24, 124) that transmits driving power from the engine to the travel device; a forward/backward travel switch operation device that receives an instruction for forward or backward travel from an operator; and a control unit configured to control the power transmission device (24, 124); wherein the power transmission device (24, 124) includes: an input shaft; an output shaft; a generator (MG1, MG2) that receives driving power from the engine; a motor (MG1, MG2) that outputs driving power to the travel device; and an energy storage unit that stores electricity generated by the generator (MG1, MG2); the power transmission device (24, 124) being configured so that a rotation speed ratio of the output shaft with respect to the input shaft is changed by changing the rotation speed of the motor (MG1, MG2); and the control unit controls the engine based on an energy management required power (Hem) and includes an energy management requirement determination unit that determines, on the basis of the difference between a target electricity storage amount (Cp_target) and a current electricity storage amount (Cp_storage) in the energy storage unit, the energy management required power (Hem) required by the power transmission device (24, 124) for charging the energy storage unit; characterized by a vehicle speed detecting unit that detects a vehicle speed of the travel device; wherein the control unit further includes an engine requirement determination unit; the energy management requirement determination unit increases the target electricity storage amount (Cp_target) when a first travel direction according to an instruction from the operator that is received from the forward/backward travel switch operation device, and a second travel direction determined from the vehicle speed detected by the vehicle speed detecting unit, are different, and the engine requirement determination unit determines an engine required power (Hdm) on basis of the energy management required power (Hem). an engine; a hydraulic pump driven by the engine; a work implement driven by hydraulic fluid discharged from the hydraulic pump; a travel device; a power transmission device (24, 124) that transmits driving power from the engine to the travel device; a forward/backward travel switch operation device that receives an instruction for forward or backward travel from an operator; and a control unit configured to control the power transmission device (24, 124); wherein the power transmission device (24, 124) includes: an input shaft; an output shaft; a generator (MG1, MG2) that receives driving power from the engine; a motor (MG1, MG2) that outputs driving power to the travel device; and an energy storage unit that stores electricity generated by the generator (MG1, MG2); the power transmission device (24, 124) being configured so that a rotation speed ratio of the output shaft with respect to the input shaft is changed by changing the rotation speed of the motor (MG1, MG2); and an input shaft; an output shaft; a generator (MG1, MG2) that receives driving power from the engine; a motor (MG1, MG2) that outputs driving power to the travel device; and an energy storage unit that stores electricity generated by the generator (MG1, MG2); the power transmission device (24, 124) being configured so that a rotation speed ratio of the output shaft with respect to the input shaft is changed by changing the rotation speed of the motor (MG1, MG2); and the control unit controls the engine based on an energy management required power (Hem) and includes an energy management requirement determination unit that determines, on the basis of the difference between a target electricity storage amount (Cp_target) and a current electricity storage amount (Cp_storage) in the energy storage unit, the energy management required power (Hem) required by the power transmission device (24, 124) for charging the energy storage unit; characterized by a vehicle speed detecting unit that detects a vehicle speed of the travel device; wherein the control unit further includes an engine requirement determination unit; the energy management requirement determination unit increases the target electricity storage amount (Cp_target) when a first travel direction according to an instruction from the operator that is received from the forward/backward travel switch operation device, and a second travel direction determined from the vehicle speed detected by the vehicle speed detecting unit, are different, and the engine requirement determination unit determines an engine required power (Hdm) on basis of the energy management required power (Hem). wherein the control unit further includes an engine requirement determination unit; the energy management requirement determination unit increases the target electricity storage amount (Cp_target) when a first travel direction according to an instruction from the operator that is received from the forward/backward travel switch operation device, and a second travel direction determined from the vehicle speed detected by the vehicle speed detecting unit, are different, and the engine requirement determination unit determines an engine required power (Hdm) on basis of the energy management required power (Hem).