In Japan, books and magazines have been distributed under the resale price maintenance and consignment sale systems. At present, the return rate of books and magazines has reached approximately 40 percent of the quantity of publications under the systems mentioned above. This is a severe problem from the viewpoints of both business and environment. For the purpose to solve this problem, a new sale system where wholesale price is reasonable while buyback price is inexpensive has been programmed and practiced. The wholesale and buyback prices are important contract parameters in the transaction program between publisher and bookstore. In this paper, the publishing supply chain consisting of a publisher and a bookstore is formulated as a mathematical model. Then, we have developed a new approach to solve the collaborative sale contract problem with wholesale and buyback prices as contract parameters.