Abstract: A protection device includes a case, an elastic plugging element and locking element. The case is formed with three holes at its three sides, two of which are arranged oppositely, and a pair of holes at its bottom. The elastic locking element located in the case having two shoulders and a waist is formed at one end a pair of claws to secure it on the case and at the opposite end a pressing end projecting out from a side hole of the case. The plugging element has two zigzag edged set legs to stick through the pair of holes at the bottom of the case. The bases of the set legs at their upper ends are spaced from each other so as to form a preparing area and they stretch horizontally to stick out from the other two opposite side holes of the case to be the other two pressing ends of the device. A waterproof rubber frame can be attached to the bottom of the case so that when the present device is in use, the frame can entirely cover the socket.