IN-VEHICLE DEVICE

An in-vehicle device includes: a parking state detector configured to detect a parking state of a vehicle; a vehicle cabin situation detector configured to detect a situation in a vehicle cabin of the vehicle; a child information detector configured to detect presence of a child and position information on the child in the vehicle cabin based on a signal from a sensor provided on a child seat in the vehicle cabin; a temperature information acquisition unit configured to acquire temperature information in the vehicle cabin; a notification unit configured to, when the child is left in the vehicle cabin, notify outside of the vehicle that leaving of the child has occurred; and a controller configured to, when the vehicle is in the parking state, control a notification mode of the notification unit according to information including the temperature information in the vehicle cabin.