The purpose of the present invention is to carry out a high-precision estimation of whether a user is engaged in solitary activity. Provided is a server 10, being an aloneness estimation device for estimating whether a user is engaged in solitary activity. The server 10 comprises: an operating state information acquisition unit 11 for acquiring operating state information indicating the state of a user's operation of a terminal 20 at each location; a reference setting unit 12 for setting, according to the locations relating to the acquired operating state information, a reference to be used in estimation; an estimation unit 13 for estimating, on the basis of the set reference and from the operating state information acquired by the operating state information acquisition unit, whether the user is engaged in solitary activity; and an output unit 14 for outputting information based on the estimation.
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