A process debug method used to identify at least one excursive machine in a manufacturing process comprising the following steps: First, a series of validity identification data is collected, and the serial validity identification data is associated with its pathway to obtain a plurality of validity identification data sequences in corresponding to the machines. Subsequently, a sorting process is conducted to cluster the validity identification data sequence into several groups, and the clustered groups are ranked into a first order. The validity identification data sequences are subjected a continuity analysis to determine the continuity of the defects occurring in a particular machine. And the continuities of the machines involved in a particular group are ranked into a second order. Accordingly, the excursive machines causing the defective end products in the manufacturing process can be identified by the way of joining the second orders according to the first order.