PURPOSE: To omit a code converter circuit at the outside and to obtain an absolute address type position detector whose entire structure is simplified, by incorporating memory element, which converts the detected code, in an absolute encoder.

CONSTITUTION: The waveform of the signal outputted from a photodiode 3 is shaped by a comparator amplifier 10. Then the signal is inputted to a memory element 11. The memory element is constituted by P-ROM. Arbitrary code data is stored and the codes of the input data are converted. The memory element 11 stores two kinds of data. For one kind of data, the addresses of the output codes are increased for the clockwise rotation of an input shaft. For the other data, the addresses are decreased. The direction is instructed by the operation from the outside of an absolute encoder. The direction instruction is inputted into an input buffer 12, and either of the data is selected. Thus the displacement increasing direction can be selected by the user.