Reducing vibration of high-rise structures under earthquake load has been the subject of considerable efforts in Japan. Relevant researches about vibration energy dissipation devices for buildings have been undertaken. An active mass damper is one of the well-known vibration control devices. Despite the accumulation of much knowledge of control design methods for the system, application of the devices to high-rise structures under earthquake load is challenging, because the active mass dampers have one serious disadvantage about stroke limitation of the auxiliary mass. In this study, we have proposed a new control system, which had a neural oscillator and position controller, to solve this problem. The main role of this neural oscillator included in newly proposed system is picking up the phase information of the eigen-frequency component of a target structure, then the auxiliary mass of an active mass damper is excited by reference to the oscillator’s signal. We can easily regulate the stroke of the active mass damper no matter how large the target structure swings, because the control signal for the auxiliary mass of the phase and amplitude information of the active mass damper are separately processed. However, there is no general determination method for the desired stroke of the auxiliary mass from the oscillator’s signal. The previous method determined the desired stroke of the auxiliary mass using two state quantities of the oscillator, which depends on types of oscillators and has non-linearity and instability. Thus, this study proposes a generation method for the desired stroke of the auxiliary mass by using synchronous detection. From the results of numerical simulation, the presenting method can apply to any types of oscillators and generate the linear and stable signal by reference to an oscillators’ signal, and was effective for improving the control performance.