PROBLEM TO BE SOLVED: To realize a fish number measuring device capable of easily counting fish at low cost. [Solution Means] The fish number measuring device 1 includes an ultrasonic wave transmitter / receiver 2 and a processing device 4. The ultrasonic wave transmitter / receiver 2 transmits an ultrasonic beam 9 into water in a first cage 11 connected to a second cage 12 via a path 13, and is composed of a single channel. The transmission / reception element is provided, and the transmission / reception element is arranged at a position where the ultrasonic beam 9 does not intersect the path 13. The processing device 4 outputs a transmission signal for driving the ultrasonic wave transmitter / receiver 2 to the ultrasonic wave transmitter / receiver 2, and based on an echo signal input from the ultrasonic wave transmitter / receiver 2 that has received the reflected wave, the processing device 4 outputs the transmission signal to the ultrasonic wave transmitter / receiver 2. The number of fish moving from the path 13 to the first cage 11 through the ultrasonic beam 9 is obtained. [Selection diagram] Fig. 1【課題】低コストで簡便に魚を数えることが可能な魚数計測装置を実現する。【解 決手段】魚数計測装置１は、超音波送受波器２と、処理装置４と、を備える。超音波送受波器２は、経路１３を介して第２生簀１２に接続された第１生簀１１に おける水中に超音波ビーム９を送波するものであって、単一のチャネルで構成される送受波素子を備え、当該超音波ビーム９が経路１３に交差しないような位置 に前記送受波素子が配置される。処理装置４は、超音波送受波器２を駆動するための送信信号を超音波送受波器２に出力し、反射波を受波した超音波送受波器２ から入力したエコー信号に基づいて、超音波ビーム９を通過して経路１３から第１生簀１１に移動する魚の数を取得する。【選択図】図１
