A server casing includes a frame and a plate connecting structure disposed in the frame and including a plate and a board. A first rivet hole of the plate has a first outer hole edge and a first inner hole edge greater than the first outer hole edge. A first guide surface connects the first outer hole edge and the first inner hole edge. The board has a board edge corresponding to the first rivet hole. A first arm is formed on the board edge. After the first arm is pressed to abut against the first guide surface, the pressed first arm deforms along the first guide surface to be located in the first rivet hole, so as to fix the board to the plate.