According the present invention, a behavior specifying device, which specifies the behavior of livestock, includes: a storage means which stores acceleration data measured by an acceleration sensor mounted on the livestock; an acquisition means which acquires, from among the acceleration data stored in the storage means, one or more pieces of acceleration data between prescribed times; an index value calculation means which calculates, from the one or more pieces of acceleration data acquired by the acquisition means, a prescribed index value; and a specifying means which specifies a behavior of the livestock on the basis of the index value calculated by the index value calculation means, and a pre-created specifying model for specifying a behavior of the livestock.
