A securing device includes a securing member defining a securing hole therein, and a fastener extending through the securing hole. The fastener includes a spring, and a bolt having a main portion, a bottom fixing portion, and a top head portion. The securing hole includes a large portion, a small portion, and a concave around the small portion. A diameter of the small portion is greater than the main portion and smaller than the fixing portion. A diameter of the large portion is greater than the fixing portion and smaller than the spring. The main portion extends through the small portion with the fixing portion tightly abutting the securing member. The spring is mounted around the main portion and received in the concave. The spring is compressed between the head portion and a step of the securing member in the concave.