A stacked flexible printed circuit board assembly with a side connection section is provided, including a first flexible printed circuit board, a second flexible printed circuit board, and a curved connection section. The curved connection section is integrally connected to and between side edges of the first flexible printed circuit board and the second flexible printed circuit board. The first flexible printed circuit board is folded in a direction toward and thus stacked on the second flexible printed circuit board such that a plurality of first contact pads of the first flexible printed circuit board correspond respectively to a plurality of second contact pads of the second flexible printed circuit board. A height adjustment layer or an adhesive layer is provided between the first flexible printed circuit board and the second flexible printed circuit board to suit the need of thickness in plugging or soldering.