An in-vehicle device is capable of coupling to a portable terminal, receives content data played by the portable terminal that has been coupled, and outputs the content data that has been received. While music is being played back by the portable terminal, the in-vehicle device estimates a remaining battery level of the portable terminal after playback of the music to be next played back finishes, and provides, when the estimated value is a threshold value or less, notification of the remaining battery level before the playback of music starts and/or after the playback finishes.