Abstract: In a production planning method, among those production step types the product procurement periods of which satisfy the desired time of delivery, allocation to production steps with longer product procurement periods is performed, in order from orders with shorter desired times of delivery; or, in a production planning method, expectation values and request values are compared, and allocation is performed; or, in a production planning method, bottleneck steps are considered, and production space and production periods are allocated. It is possible to provide a production planning method and system which are objective even for products subject to trends in popularity and demand for which fluctuates, and conventional production planning for which relied on human experience and intuition and was not thought to be adequately handled by a computer system. Also, allocation of production space upon receipt of an order can be performed efficiently and promptly.