We previously proposed a meeting scheduling system based on mobile agent technology. The users of our system do not need to input all of their schedules unlike the existing groupwares. When a user intends to call a meeting, he only inputs information about the meeting. On behalf of the inviter, mobile agents move around each invited user's computer to ask whether he can join the meeting and negotiate with him if necessary. In this paper, we propose a NAT traversal method for a meeting scheduling system based on mobile agent technology. In our former system, the users inside a NAT network cannot use the system because mobile agent cannot migrate from outside the NAT network to inside NAT network. For this reason, our proposed system does not work with some network including a NAT router, such as a home network and an office network. To solve this problem, we implemented a new migration method for mobile agents.