An exemplary motherboard fixing device is for fixing a motherboard onto a case plate inside a computer case. The motherboard fixing device is fixable on the case plate, and includes a first fixing strip and a second fixing strip. The first fixing strip includes a first, second, and third flat plates. The second flat plate is between the first and third flat plates. The first and second flat plates cooperatively define a slide groove for receiving an edge of the motherboard. The second fixing strip includes a bottom plate and a lateral plate. The third flat plate and the bottom plate include first latch hooks. The first latch hooks is engagable in corresponding through holes of the case plate, such that the first and second fixing strips are fixed on the case plate. The lateral plate includes second latch hooks for being latchable on an opposite edge of the motherboard.