A USB memory stick includes a metal shell structure defining opposing top opening and bottom opening and a locating hole, a PC board formed of a USB interface circuit and a memory chip package, and a tray, which includes a support panel supporting the PC board, a clip extended from one side of the support panel and clamped on the memory chip package of the PC board, a spring plate extended from the clip and pressed on the PC board against the support panel, and an oblique retaining leaf obliquely extended from the spring plate and engaged into the locating hole of the metal shell structure.