Cap structure and keyswitch thereof

A keyswitch comprising:

• a bottom board;
• a lifting mechanism disposed on the bottom board;
• and
• a cap structure combined with the lifting mechanism to be movable between a pressed position and a non-pressed position, the cap structure comprising:
• a cap having a top surface, a bottom surface and an engaging structure, the top surface and the bottom surface being opposite to each other, the engaging structure protruding from the bottom surface to be engaged with the lifting mechanism;
• a first circuit laid out on the top surface for connecting to a sensing device or a display device attached on the top surface;
• a second circuit laid out on the bottom surface, the second circuit avoiding the engaging structure and passing through the cap to be connected to the first circuit;
• and
• a flexible circuit board connected to the second circuit for performing signal transmission of the sensing device or the display device via the first circuit and the second circuit.