A control device that is communicably connected to a vehicle includes a control unit. The control unit executes acquisition of sensor information from a sensor provided in the vehicle, determination of whether the vehicle is parked based on the sensor information, determination of whether a user is staying in the vehicle based on the sensor information, and estimation that the user is staying in the vehicle when a parking time of the vehicle exceeds a first reference value and a staying time of the user exceeds a second reference value.