In a network connecting device connectable to a network, a connection approval/disapproval determination section determines approval/disapproval of connection to a network in accordance with a connection approval/disapproval determination rule managed by a connection approval/disapproval determination rule management section. When there is a security problem in a content of the connection approval/disapproval determination rule if a connection is to be formed, the security problem is solved by having a user re-input authentication information in the content of the connection approval/disapproval determination rule.