Abstract: A leak-detecting shut-off device has a holding mount, a valve seat and an operating set. The holding mount has a connecting segment, a mounting segment, an expansion element and a pushing rod. The expansion element is mounted in the mounting segment. The pushing rod is mounted in the mounting segment, is mounted around the expansion element, and has a mounting cover and multiple pushing panels. The valve seat is connected to the holding mount and has a body, an inlet pipe and an outlet pipe. The body is mounted in the connecting segment and has two connecting boards. The operating set is connected to the valve seat and has a valve shaft, a spring and an operating tab. The valve shaft is movably mounted in the body. The operating tab is connected to the connecting boards, is selectively moved above the pushing rod and abuts against the valve shaft.