A protection casing of an electronic device with a function of supporting includes a lower casing having an approximately rectangular shape; a periphery of the lower casing being formed with a frame for enclosing a tablet computer; a supporting sheet including at least one kind of foldable traces; the supporting sheet being foldable along the foldable traces so as to present a three dimensional structure; a combining band (201) formed at an upper side of the supporting sheet adhering the supporting sheet to the lower casing; and wherein after assembly the supporting sheet to the lower casing, the supporting sheet can be folded along the foldable traces to form as a seat for standing the lower casing; and an electronic device can be placed on the lower casing for supporting the casing thereon.