To provide an ultrasonic digitizer device which detects and calculates the absolute time difference data on the transmission of ultrasonic signals, corrects the sound wave transmission velocity and also attains the digitized input on a free plane.

This digitizer device consists of a digitizer pen part 1 which includes a reference signal generation means that generates a reference signal, i.e., the reference of coordinate signals, an ultrasonic wave output element 14 and a 2nd communication transmitting means 16, ultrasonic wave receiving elements 2a and 2b which receive the coordinate signals, a 2nd communication receiving element 3 which receives the reference signal, and a digitizer control part 5 which includes a reference signal generation means, plural coordinate signal detection means, a time difference calculation means which calculates and outputs the time difference data, a distance calculation means which calculates the distance data from the time difference data and a coordinate calculation means which calculates and outputs the coordinate data on the part 1.