A communication assistance device (10) includes a communication level determination unit (11) so as to determine a level of a relationship between users who communicate with each other. The communication level determination unit (11) determines the level (communication level) of the relationship between the users based on similarity between the users obtained from preference information showing preferences of the users, and on user action records showing records of actions taken by a certain user toward a partner user with whom the certain user communicates out of the users.