An aloneness estimation device estimating whether a user acts alone includes an operation state information acquisition unit configured to acquire operation state information indicating the user's operation state of a terminal per position, a criteria setting unit configured to set criteria for use in estimation in accordance with a position related to the acquired operation state information, an estimation unit configured to estimate whether the user acts alone from the operation state information acquired by the operation state information acquisition unit based on the set criteria, and an output unit configured to output information in accordance with estimation.