A device for mounting a riser card includes a base board forming two rods, a motherboard forming an expansion slot to connect the riser card, and a fixing member having two legs at opposite ends. The rods extend through the motherboard and are positioned at opposite ends of the expansion slot. Each rod contains a resilient member inside, and a ball mounted to the resilient member and partly extending out of the rod. The riser card is fixed to the fixing member. Each leg defines a cylindrical hole fitted about one of the rods. The balls partly extend out of the corresponding rods and block tops of the corresponding legs.