1. A method of notification by which questions and answers are exchanged between users, comprising: a question-processing step of receiving registration of a question from a questioner who is included among the users, and publishing the registered question; an answer-processing step of receiving registration of one or more answers to the question from one or more respondents who are included among the users, and publishing the registered answer(s); a designation-receiving step of receiving, from one or more referring users who are included among the users but are not the respondent(s), designation of a question that is among the published question(s) and that the referring user(s) has interest in; and an answer notification step of notifying the referring user(s) of the one or more answers to the designated question.