A built-in inter-dental brush and a visual inter-dental brush. The built-in inter-dental brush comprises an inter-dental brush (1) and a delivery device (2). The inter-dental brush (1) is movably built in a bent tube (21-1) at the front end of the delivery device (2). After a guiding head (21) is aligned with a slit between the teeth, a sliding mechanism (22) on the delivery device (2) is pushed to drive a working portion (11) of the inter-dental brush to be automatically bent along the radian of the bent tube, aligned with the slit between the teeth and enter the slit. A sliding block (22-2) on the sliding mechanism (22) of the delivery device is pushed and pulled back and forth to enable the working portion (11) of the inter-dental brush to move back and forth in the slit and clean the slit. The visual inter-dental brush comprises an inter-dental brush (1) and a delivery device (2). The delivery device (2) is provided with a guiding head (21), a housing (23) and an illuminating system (24). The inter-dental brush (1) is mounted on the guiding head (21). The illuminating system (24) can provide illumination to the inter-dental brush. The visual inter-dental brush also comprises an observing system (25) that is an observing mirror or a photographing system.
