A positioning apparatus includes a computer chassis and a positioning device. The computer chassis secures a plurality of expansion cards and includes a cover. The cover comprises a first flange and a second flange opposite to the first flange. The positioning device includes a securing member and a positioning member secured to the securing member. The securing member is secured to the first flange and a second flange. The positioning member is pressed on the plurality of expansion cards to prevent the plurality of expansion cards from moving.