A flexible printed circuit board structure includes a spiral flexible printed circuit board and a protection cover capable of providing functions of extensibility and retractility. The spiral flexible printed circuit board includes a flexible substrate curling up spirally, a patterned circuit layer and a plurality of electrical contacts. The patterned circuit layer is disposed on the flexible substrate. The electrical contacts are disposed on an end of the flexible substrate and electrically connected to the patterned circuit layer. The protection cover at least covers a part of the spiral flexible printed circuit board.