A parking sensor apparatus has a microprocessor and multiple ultrasonic sensors. The microprocessor uses a time division transmitting method to control only one ultrasonic sensor to output an ultrasonic detecting signal. In addition, after one ultrasonic detecting signal is output, all ultrasonic sensor are controlled to be in receiving status. Therefore, the microprocessor receives the reflected detecting signals from the ultrasonic sensors and obtains preset distances defined between adjacent ultrasonic sensors to calculate the shortest distance between the vehicle and the obstacle. Further, since only one ultrasonic sensor outputs the ultrasonic detecting signal at a time point, the microprocessor clearly determines that the reflected detecting signal is corresponding to the present ultrasonic sensor, that is controlled to output the ultrasonic detecting signal.