The invention relates to a waiting time predicting method for a queuing machine. The waiting time predicting method comprises following steps of collecting historical arriving moments of customers, the line lengths at the arriving moments of the customers and waiting time in a plurality of historical service periods, generating a customer waiting time table, recording the arriving moments of the customers and the line lengths at the arriving moments of the customers when the customers arrive, acquiring information about the customers required to wait in line, counting the waiting time of the customers by virtue of the customer waiting time table, then acquiring information about one queued customer accepting the service, recording actual waiting time of the queued customer, recounting the waiting time of the rest queued customers, and carrying out cyclic operation until the last service period ends. The waiting time predicting method has the advantages that the accuracy is high, a prediction error is avoided, the customers can conveniently and reasonably arrange the time, and the time availability is improved; meanwhile, the waiting time can be corrected according to queuing information of the customers at any time, so that the customers cannot miss service chances, and the vacant number rate is decreased.