Provided is an estimating device, an estimating method, and an estimating program that each make it possible to estimate the area of activity of a target user with a smaller amount of information. An estimating device includes a first position distribution generating unit configured to generate a first position distribution of a target user on social media based on account information of the target user, a second position distribution generating unit configured to generate a second position distribution of a friend who is friends with the target user on the social media based on account information of the friend, and an estimating unit configured to estimate an area of activity of the target user based on the generated first position distribution and the generated second position distribution.