In this paper, we propose a decomposition and coordination method for timed Petri Nets to determine an optimal firing sequence to minimize the given objective function. The timed Petri Net is decomposed into several subnets in which the optimal firing sequence for each subnet is easily solved by Dijkstra's algorithm in polynomial computing time. The proposed method is applied to a flowshop scheduling problem. The effectiveness of the proposed method is confirmed by comparing the performance between the simulated annealing method.