Digital data obtained by converting, by an A/D converter, an angular velocity measured by a sensor is transmitted from a remote control to a game machine. A CPU of the game machine corrects the digital data. That is, the CPU sequentially stores sequential digital data in a buffer. A stable range (d1-d2) in which each digital data can be defined to be stable is calculated for the latest digital data. An average value of those of the digital data stored in the buffer that are consecutively present in the stable range retrogressively from the latest digital data is calculated. Using the average value, the latest digital data is corrected.