To provide a theft detection device that can properly obtain theft information while preventing theft's notice, and to provide vehicle-mounted equipment.

The theft detection device includes: a theft detection part 21 detecting that the vehicle-mounted equipment 20 mounted to a vehicle 10 is robbed; and a controller 23 obtaining the theft information which is information related to the theft during a normally operable state by allowing the normal operation of the vehicle-mounted equipment when the theft is detected.