A positioning device for fixing an interface card on a computer casing without using screws, is composed of a vertical wall board of a computer casing, which is provided with long through-holes; fixing seats, which are connected on an interface of the vertical wall board, and are provided with shaft holes and one movable groove; elastic members, which are provided with shaft holes and spring leaves, and are emplaced into the movable grooves; a shaft, which is connected on the fixing seats and the elastic members; and an interface card is provided with a cover, with an end of the cover being provided with an outer board. When the elastic member is subjected to force to rotate, the spring leaf will be abutted on the outer board. When the elastic member rotates reversely, the spring leaf will be escaped from the outer board, and the cover and the interface card can be removed from the vertical wall board simultaneously.