The present invention relates to an adjustable protective cover for electronic device that is consists of a front cover and a back cover; wherein the front cover and the back cover are connected and are capable of folding to cover and contain an electronic device. The inner surface of the back cover is a surface capable of being stuck and fixed that allows at least two independent corner covers to be fixed thereon. The independent corner cover has a base seat, whereon a fixing strip is disposed to fit with a corner of electronic device body. The independent corner cover is capable of adjusting the sticking position according to the size of electronic device in order to contain and protect electronic device bodies of different sizes.