A speed change control system for a vehicle (EV, HV), comprising: a transmission (4, 13); a drive wheel that is connected to the transmission (4, 13); a motor (1, 11) in which at least any one of a torque and a speed is changed by changing a speed ratio of the transmission (4, 13); an electric storage device that is connected to the motor (1, 11); and a controller that controls the transmission (4, 13), wherein the controller is configured to select a shifting mode of the transmission (4, 13) from a first mode in which a speed ratio of the transmission (4, 13) is changed in accordance with an operating condition of the vehicle (EV, HV), and a second mode in which the speed ratio of the transmission (4, 13) is fixed to a predetermined ratio, select the first mode in a case that a state of charge level of the electric storage device is lower than a predetermined level, and select the second mode in a case that the state of charge level of the electric storage device is equal to or higher than the predetermined level, and select the shifting mode of the transmission (4, 13) from a normal shifting mode in which the speed ratio of the transmission (4, 13) is controlled in accordance with a vehicle speed and a required drive force to optimize a system efficiency, and a seamless priority mode in which the speed ratio of the transmission (4, 13) is controlled to change a drive torque quickly in response to an operation of an accelerator to reduce a change in a behavior of the vehicle (EV, HV) resulting from execution of the shifting operation, wherein the seamless priority mode includes the first mode and the second mode, and the first mode includes a mode in which at least any one of the speed ratios available in the normal shifting mode is inhibited, characterized in that the controller is further configured to calculate an increasing amount of an energy loss resulting from propelling the vehicle (EV, HV) in the seamless priority mode, calculate a difference between an amount of regenerative energy by the motor (1, 11) in a case of maintaining the current speed ratio during deceleration of the vehicle (EV, HV), and an amount of regenerative energy by the motor (1, 11) in a case of changing the speed ratio of the transmission (4, 13) to increase the regenerative energy, allow execution of a speed change operation of the transmission (4, 13) during deceleration of the vehicle (EV, HV) in a case that the difference between the regenerative energies is greater than the increasing amount of the energy loss, and inhibit execution of a speed change operation of the transmission (4, 13) during deceleration of the vehicle (EV, HV) in a case that the difference between the regenerative energies is smaller than the increasing amount of the energy loss. a transmission (4, 13); a drive wheel that is connected to the transmission (4, 13); a motor (1, 11) in which at least any one of a torque and a speed is changed by changing a speed ratio of the transmission (4, 13); an electric storage device that is connected to the motor (1, 11); and a controller that controls the transmission (4, 13), wherein the controller is configured to select a shifting mode of the transmission (4, 13) from a first mode in which a speed ratio of the transmission (4, 13) is changed in accordance with an operating condition of the vehicle (EV, HV), and a second mode in which the speed ratio of the transmission (4, 13) is fixed to a predetermined ratio, select the first mode in a case that a state of charge level of the electric storage device is lower than a predetermined level, and select the second mode in a case that the state of charge level of the electric storage device is equal to or higher than the predetermined level, and select the shifting mode of the transmission (4, 13) from a normal shifting mode in which the speed ratio of the transmission (4, 13) is controlled in accordance with a vehicle speed and a required drive force to optimize a system efficiency, and a seamless priority mode in which the speed ratio of the transmission (4, 13) is controlled to change a drive torque quickly in response to an operation of an accelerator to reduce a change in a behavior of the vehicle (EV, HV) resulting from execution of the shifting operation, wherein the seamless priority mode includes the first mode and the second mode, and the first mode includes a mode in which at least any one of the speed ratios available in the normal shifting mode is inhibited, characterized in that the controller is further configured to calculate an increasing amount of an energy loss resulting from propelling the vehicle (EV, HV) in the seamless priority mode, calculate a difference between an amount of regenerative energy by the motor (1, 11) in a case of maintaining the current speed ratio during deceleration of the vehicle (EV, HV), and an amount of regenerative energy by the motor (1, 11) in a case of changing the speed ratio of the transmission (4, 13) to increase the regenerative energy, allow execution of a speed change operation of the transmission (4, 13) during deceleration of the vehicle (EV, HV) in a case that the difference between the regenerative energies is greater than the increasing amount of the energy loss, and inhibit execution of a speed change operation of the transmission (4, 13) during deceleration of the vehicle (EV, HV) in a case that the difference between the regenerative energies is smaller than the increasing amount of the energy loss.