A keyswitch includes a circuit board, a bottom board abutting against the circuit board, a cap, a light receiver and a light emitter disposed on the circuit board and opposite to each other, a base disposed on the circuit board, a cover disposed on the base, a first elastic member disposed through the cover and the base, a support device, and a second elastic member fixed to the base and having a flexible rod. The support device is movably connected to the cap and bottom board and has a sheet structure. When the cap is pressed, the sheet structure blocks light transmission between the light emitter and the light receiver to generate a triggering signal. When the cap is pressed to make the flexible rod deform downward with the sheet structure and then cross the sheet structure, the flexible rod is released to collide with the cover to make sound.