Multiple suppliers can reduce the total of inventory related cost and delivery cost by cooperating their delivery schedules to a large end-user such as an auto assembly manufacturer or a big department store. In this study, two important decisions are investigated; the first one is how to decide their delivery schedules to minimize the their cooperative total cost, and the next one is allocation of the reduced cost (joint profit) to each supplier by his contribution to joint profit. A mathematical model is developed to find the delivery schedules and the common period of delivery. Moreover, the contribution to joint profit is decided by the Shapley value which is one way to distribute the joint profit to the suppliers, assuming that they all collaborate. A numerical example about allocation of the reduced cost to each supplier is presented at last.