1. An action history search device, comprising: an inquiry processing unit that receives an inquiry from a user and outputs an inquiry time, at which the inquiry is received, and a target of inquiry; a decision unit that decides a range for searching action history information, which represents history of the user's action together with a time of the user's action, using the target of inquiry; a calculation unit that calculates an elapsed time from the time of user's action, which is represented by the action history information within the range, to the inquiry time; a judgment unit that judges, using the elapsed time and a narrowing-down model, a probability on each response candidate to the inquiry based on the history of the action represented by the action history information within the range, the narrowing-down model being used for judging according to the elapsed time the probability that the response candidate to the inquiry, which is obtained from the history of the action represented by the action history information, is the user's desired response; and an output unit that outputs the response candidate according to the probability.