PROBLEM TO BE SOLVED: To more reliably detect behaviors such as rumination and foraging in each livestock cattle. A behavior detection device is a behavior detection device that detects the behavior of a domestic cattle 31 including a first transmitter 21 and a second transmitter 22. The first transmitter 21 is swayably suspended from the first sword 63 and the first sword 63, which are hung from the bridle of the livestock cow 31, and generate electric power by the sway. A first beacon transmitter 61 that transmits a first count value for counting the number of activations and a first identification information for identifying the livestock cow 31 is provided. The second transmitter 22 is swayably suspended from a second iron 73, which is suspended and mounted on the collar 42 of the livestock cow 31, and a second iron 73, and generates electric power by the rocking. A second beacon transmitter 71 for transmitting a second counting value for counting the number of activations and a second identification information for identifying the livestock cow 31 is provided. [Selection diagram] Fig. 2【課題】家畜牛それぞれに、より確実に、反すうや採食などの行動を検出する。【解決手段】行動検出装置は、第１の発信機２１と第２の発信機２２とを含む家畜牛３１の行動を検出する行動検出装置である。第１の発信機２１は、家畜牛３１の頭絡に吊り下げられて装着される第１の鐶６３と、第１の鐶６３に揺動可能に吊り下げられ、揺動によって電力を発生し、起動の回数を計数した第１の計数値および家畜牛３１を識別するための第１の識別情報を発信する第１のビーコン発信器６１とを備える。第２の発信機２２は、家畜牛３１の首輪４２に吊り下げられて装着される第２の鐶７３と、第２の鐶７３に揺動可能に吊り下げられ、揺動によって電力を発生し、起動の回数を計数した第２の計数値および家畜牛３１を識別するための第２の識別情報を発信する第２のビーコン発信器７１とを備える。【選択図】図２
