The present invention provides a vehicle-mounted audio device including a casing, a tuner, an audio output unit, a housing chamber, an opening of the housing chamber, a housing, a lock mechanism, and a casing connector. The tuner is disposed in the casing. The audio output unit is for amplifying and outputting an audio signal supplied from the tuner. The housing chamber is defined in the casing. The opening is defined in a front panel of the casing. The housing is for accommodating a portable audio device. The housing is removably housed in the housing chamber through the opening. The lock mechanism is for selectively locking the housing in the housing chamber and unlocking the housing from the housing chamber. The casing connector is electrically connected to the audio output unit and disposed in the housing for disengageably connecting to an audio signal output connector of the portable audio device.