South and North Korea have been intermittently discussing confidence building and arms reduction since the end of the Korean War, but they are practically continuing to increase their military capabilities. Armament competition due to increased military power cannot be ignored, not only hindering economic development but also political and social costs. These costs will grow over time and the cost of reunification will come as an unaffordable burden given the unification of the two Koreas. The unification of the Korean Peninsula can end the history of division, thereby promoting the prosperity of the Korean people and contributing to world peace. However, unification can cause various problems, including the cost of the two Koreas' economic power differences and social chaos. From this point of view, the financial burden could be reduced if the cost of reunification is calculated, financed and prepared. To illustrate these problems, this paper calculated the approach and cost of arms reduction from the perspective that budget savings for the procurement of unification costs could contribute to some extent by the reduction of armaments. The budget saved by the reduction of military expenditure explained the impact on the unification cost compared to the unification cost, and proposed a plan to accumulate the savings from the reduction of military expenditure and use it as the unification cost in the future.