A circuit board structure has a first flexible circuit board, a second flexible circuit board, and a rigid board structure. The first flexible circuit board has a first dielectric layer and a first conductive circuit. The second flexible circuit board has a second dielectric layer and a second conductive circuit. The rigid board structure connects the first flexible circuit board and the second flexible circuit board. The rigid board structure has a third dielectric layer and a third conductive circuit. A dielectric loss value of the third dielectric layer is less than that of each of the first dielectric layer and the second dielectric layer. The third conductive circuit is electrically connected to the first and second conductive circuits.