The present disclosure provides a motor drive device and a motor drive system for improving a control stability despite an imbalance in zero crossing points in a sensorless motor of which position of a rotor is estimated by a counter electromotive force. The motor drive device includes: a position detector configured to detect a rotational position of a rotor of a motor by detecting a plurality of zero crossing points of a counter electromotive force induced in the motor; and a controller configured to control the motor by estimating a phase change timing based on a time interval between a current zero crossing point and a previous zero crossing point of a same state as the current zero crossing point among the plurality of zero crossing points detected by the position detector.