The present invention realizes a new actuated valve type water flow detection device that can be applied to a pipe with a relatively large bore diameter. The water flow detection device A includes a coil spring for urging a detection rod in an opening direction of a valve body. Therefore, while detecting water flow by linking a rotation of the detection rod 11 to a rotation of the valve body when the valve body opens or closes by a differential pressure, the detection rod does not apply a closing load to the valve body that is released. Therefore, even when the rotation of the valve body is small because the water flow in the secondary side is small in a conventional actuated valve type water flow detection device, it is possible to increase an opening angle of the valve body.