An in-wall video/audio signal adapter device including a first adapter and a second adapter. The first adapter includes a transmitter unit fixed on a mount. The mount can be locked in a first cavity previously formed on a wall. The second adapter includes a receiver unit fixed on a mount. The mount can be locked in a second cavity previously formed on the wall. CAT5/CAT6 Internet signal transmission cables are previously embedded in the wall. The Internet signal transmission cables are connected between the first adapter and the second adapter.