A position information providing apparatus for providing present position information to a position notifier apparatus is provided. The position information providing apparatus includes an ultrasonic wave output device for outputting ultrasonic wave and a controller for controlling the ultrasonic wave output device. In accordance with contents of the present position information, the controller sequentially selects a modulation frequency from among multiple detectable frequencies which are detectable by the position notifier apparatus and which are lower than an ultrasonic wave frequency. The controller controls the ultrasonic wave output device so that a maximum value or a minimum value of amplitude of the ultrasonic wave varies with to the selected modulation frequency.