To provide an air valve which can be detected that a pipeline is full at a place away from the pipeline.

An air valve comprises a communicating hole 2 formed at a lower portion to be communicated with a pipeline, and in a valve casing 1 having a large air hole 3 formed at an upper portion, a floating valve element 5 opening and closing the large air hole 3 and a valve element of float 7 opening and closing the floating valve element 5 are disposed to be capable of moving up and down. The large air hole 3 is covered with a cover 1a having a limit switch 10. The limit switch 10 is engaged with a cam 8 which is inserted into a through hole 1b formed at the cover 1a and the large air hole 3 to be disposed to the floating valve element 5. Therefore, the cam 8 lifted according to closing of the floating valve element 5 operates the limit switch 10, so that an operation manager can detect that a pipeline is full at a place away from the pipeline.