An adapter assembly, comprising: a casing comprising a plurality of side walls, a front cover and a rear cover, wherein the plurality of side walls are connected with each other and disposed between the front cover and the rear cover, the plurality of side walls, the front cover and the rear cover collaboratively define an accommodation space located in the casing, the front cover comprises an opening, a plurality of concaves and a plurality of position-limiting portions, the opening is in communication with the accommodation space, the plurality of concaves are concavely formed from an inner surface of the opening, the plurality of position-limiting portions are disposed on the inner surface of the opening of the front cover, each of the plurality of position-limiting portions is extended from the inner surface of the opening toward a center of the opening, and the plurality of position-limiting portions and the plurality of concaves are arranged alternately; and a plug adapter detachably assembled with the casing and comprising a main body and a plurality of protrusions, wherein the plurality of protrusions are disposed on an outer surface of the main body, and the plurality of protrusions are corresponding in position to the plurality of concaves in a one-to-one relationship; wherein when the plug adapter is assembled with the casing, portion of the main body is disposed in the accommodation space, the other portion of the main body penetrates through the opening and is exposed to the exterior of the accommodation space, each of the plurality of protrusions penetrates through corresponding one of the plurality of concaves and is exposed to the exterior of the accommodation space, and each of the plurality of protrusions exposed to the exterior of the accommodation space is connected with corresponding one of the plurality of position-limiting portions through the rotation of the plug adapter so that the plug adapter is assembled with the casing. a casing comprising a plurality of side walls, a front cover and a rear cover, wherein the plurality of side walls are connected with each other and disposed between the front cover and the rear cover, the plurality of side walls, the front cover and the rear cover collaboratively define an accommodation space located in the casing, the front cover comprises an opening, a plurality of concaves and a plurality of position-limiting portions, the opening is in communication with the accommodation space, the plurality of concaves are concavely formed from an inner surface of the opening, the plurality of position-limiting portions are disposed on the inner surface of the opening of the front cover, each of the plurality of position-limiting portions is extended from the inner surface of the opening toward a center of the opening, and the plurality of position-limiting portions and the plurality of concaves are arranged alternately; and a plug adapter detachably assembled with the casing and comprising a main body and a plurality of protrusions, wherein the plurality of protrusions are disposed on an outer surface of the main body, and the plurality of protrusions are corresponding in position to the plurality of concaves in a one-to-one relationship; wherein when the plug adapter is assembled with the casing, portion of the main body is disposed in the accommodation space, the other portion of the main body penetrates through the opening and is exposed to the exterior of the accommodation space, each of the plurality of protrusions penetrates through corresponding one of the plurality of concaves and is exposed to the exterior of the accommodation space, and each of the plurality of protrusions exposed to the exterior of the accommodation space is connected with corresponding one of the plurality of position-limiting portions through the rotation of the plug adapter so that the plug adapter is assembled with the casing.