PURPOSE: To detect the moving speed of an optical recording medium accurately and to realize stabilized information reproduction.

CONSTITUTION: An optical card 1 is relatively moved with respect to an optical head 2, and information recorded in the optical card 1 is reproduced. The time interval between the bits corresponding to the recording in the optical card 1, which is detected by the optical head 2, is measured by a bit-interval measuring circuit 16 and stored in a memory 17. The minimum bit interval 1.5T is extracted by a CPU 18 by using the data line stored in the memory 17, The speed fluctuation of the optical card 1 with respect to the optical head 2 is obtained baded on the extracted minimum bit interval 1.5T. The measured data line is corrected based on the speed fluctuation.