Abstract: An information processing device to which data can be input by the use of a rotary bezel. A pulse-count detection sensor unit 32 and a rotational-direction detection sensor unit 33 read an optical pattern which is formed on the rotary bezel to generate a series of pulse signals. The pulse-count detection sensor unit 32 and the rotational-direction detection sensor unit 33 are arranged such that a phase difference occurs between the signals of the sensor unit 32 and the signals of the sensor unit 33, so that it is possible to detect the rotational direction of the rotary bezel. A data-signal generating element 81 generates a data signal on the basis of the detected rotational angle and the pulse count generated by the pulse-count detection sensor unit 32.