The invention provides an automatic diaper side leakage detecting device which comprises a detector, a detecting liquid bucket, a detecting liquid pipe, a detecting bracket and a detecting model. The liquid inlet of the detecting liquid pipe is connected with a water pump. The water pump is arranged at the bottom of the detecting liquid bucket. The detector is provided with a flow control mechanism which runs through the detecting liquid pipe. The liquid outlet of the detecting liquid pipe is located between the front of the detecting model and the front of a diaper to be detected. A PLC controller is arranged in the detector. The detecting liquid pipe is provided with a liquid sensor. The flow sensor is connected with the signal input end of the PLC controller. The control end of the PLC controller is connected with a flow control mechanism. According to the invention, whether the to-be-detected diaper after absorbing set detection liquid volume laterally leaks; the side leakage prevention performance of the diaper is well detected; the device has the advantages of simple structure, convenient operation, high automation degree, high detection efficiency and low detection cost, and uses the PLC controller to control the flow control mechanism.