Abstract: A monitoring device has a processor configured to detect surrounding objects of specified types present within a predetermined region around a vehicle, decide a level of monitoring of surroundings by a driver, set an inattention threshold to a first value as a reference for the level of monitoring of the surroundings by the driver when the number of surrounding objects is less than an object number threshold, and set the inattention threshold to a second value that is smaller than the first value when the number of surrounding objects is equal to or greater than the object number threshold, determine whether or not the level of monitoring of the surroundings has exceeded the inattention threshold, and give the driver a warning to direct the driver's attention to the vehicle surroundings when the level of monitoring of the surroundings has exceeded the inattention threshold.