Provided is a method and system for building a user confidence. A user confidence building method of a computer apparatus including at least one processor may include storing a confidence assigned to each of users; monitoring an activity of each of the users in a service; adjusting a confidence of a first user based on an incoming edge of the first user that is formed by an activity of a second user for the first user; and propagating the adjusted confidence of the first user based on an outgoing edge of the first user in response to adjusting the confidence of the first user.