Security development project planning is a tricky task because a security manager is not sure about what combination of effective safeguards should be implemented to prevent threats from occurring and damaging future business continuity. Such the decision making problem is necessarily accompanied with investment constraints (e.g. limited budget, positive return requirement, implementation advices). Thus, it is not easy to justify a security investment plan having the several constraints. In this paper, we model the constraints and formulate the decision making problem to find the best solution by using Integer Programming.