An accompaniment determination apparatus includes a past sensor information memory configured to store past sensor information, the past sensor information acquired by sensors respectively worn by two or more users, a sensor information receiver configured to receive sensor information from the sensor worn by each of two or more users, an accompanying user determiner configured to determine at a determination time point whether two or more users are accompanying each other, using the past sensor information and the received sensor information, and an output unit configured to output information indicating a result of the determining. The accompaniment determination apparatus thus determines on a real-time basis whether the two or more users are accompanying each other using the sensor information without collecting position information.