A storage module double-layer positioning device set includes a storage module and two positioning devices arranged on two sides of the circuit board of the storage module in a staggered manner. Each positioning device includes a base with an accommodating chamber, two slideways, two side guide plates, a limiting groove, a blocking wall, a positioning block and a positioning unit; a retaining member having a horizontal portion with a pushing portion and an operating portion, a vertical portion extending inserted into the accommodating chamber, a connecting plate connected to the vertical portion, and two positioning blocks respectively inserted into the limiting grooves of the base to form positioning; an elastic member set in the accommodating chamber and stopped between the vertical portion and the blocking wall; and a sliding shaft running through the connecting plate and the elastic member with two opposite ends thereof respectively positioned in the two slideways.