A card fixer is suitable to assist a card to be fixed in a slot of an electronic device. The card fixer includes a body and a clipping structure, wherein the body has a first side and a second side parallel to the first side. A hook is disposed on the first side of the body. The clipping structure extends out of the second side of the body for clipping the card thereon. When the clipping structure of the card fixer clips the card and the assembly of the card fixer with the card is inserted into the slot, the hook is locked on an inside wall of the slot.