The invention discloses a car-mounted ETC device comprising a shell. An ETC clamping groove is formed in the shell. The car-mounted ETC device further comprises a cover plate. One side of the cover plate is rotationally connected to the shell through a rotating shaft. The cover plate has the bonding position and the clamped-connection position on the rotating stroke. At the bonding position, the inner side face of the cover plate is attached to the outer side face of the shell, and the side, away from the rotating shaft, of the cover plate is connected to the shell through a locking piece; andat the clamped-connection position, the 40-80-degree included angle is formed between the cover plate and the outer side face of the shell; clamped-connection openings are formed in the cover plate and comprise abdomen parts and opening parts; first limiting pieces are configured to be two side faces and can swing within a preset range, and are connected into the clamped-connection openings in aclamped mode; at the clamped-connection position, the bottom of a groove of the first limiting piece is used for being connected with a connecting rod of a rearview mirror in a car in a clamped mode;and a bonding layer is arranged on the outer side face of the cover plate, and a protective film is arranged on the bonding layer. According to the car-mounted ETC device, different mounting tendencies of a car owner and the car can be met simultaneously.