A foldable baffle structure is mounted to a tray of a scanner or a printer. The foldable baffle structure includes two limiting components mounted to the tray. Each limiting component includes a sliding element, a stopping element, a guiding element and a pivoting element. Middles of the two sliding elements of the two limiting components have two accommodating spaces penetrating through top surfaces and bottom surfaces of the two sliding elements. The two stopping elements of the two limiting components are mounted in the accommodating spaces of the two limiting components. A middle of one end surface of the stopping element protrudes outward to form a pivoting portion. The guiding element is mounted around an outside of the pivoting portion. The pivoting element is pivotally disposed in the stopping element.