This paper uses a standard non-cooperative sequential game with two homogeneous players to analyze investment options of groundwater development project in South Korea’s Jeju island. The model is constructed as an option game taking the uncertainty of water price and the irreversibility of investment into account. The results show that the threshold water price of follower increases with the investment scale of both the leader and the follower while the threshold water price for the leader decreases as the investment scale of the leader increases. This makes the leader choose strategies to maximize the amount of groundwater extraction regardless of the follower’s strategy. Based on the results, it is recommended for policymakers to manage sustainable use of groundwater based on the policy measures such as the groundwater extraction quota system.