Abstract: In order to create, in real time, a production plan capable of responding to a sudden plan change in consideration of costs arising due to the production plan and a failure probability of a manufacturing process, a production plan management device includes: a communication unit configured to acquire product order information including a customer request for a first product and cost criterion information specifying a cost criterion for a budget of costs required to manufacture the first product; a storage unit configured to store at least a structural constraint database including structural constraint information specifying a structural constraint defining a condition for manufacturing processes to manufacture the first product in a factory; and a production plan generating unit configured to generate, in real time, a production plan that satisfies the customer request, the cost criterion, and the structural constraint and defines manufacturing processes for manufacturing the first product.