To make it possible to read individual pieces of dispersedly stored bit data by one time of access, by decomposing plural pieces of the bit data comprising plural pieces of bits to individual pieces of bit data and dispersedly storing the same on an optical information recording medium.

This optical information recorder 1 has a writing data decomposing processing section 12, which decomposes the input data 11 to one-bit data, a writing signal control section 13, which executes the writing control of the deblocked one-bit data and a bit data writing laser 14, which writes individual pieces of the bit data to the optical information recording medium 2. The optical information reproducing device 3 has a laser 31 for reading-out the data which allows an optical sensor 32 to read the information recorded to the recording medium 2 by irradiation with a laser beam, a read-out signal control section 33 which executes the signal control of the information read by this optical sensor 32 and a read-out data synthesis processing section 34, which forms read-out data 35 by synthesizing individual pieces the bit data controlled by this read-out signal control section 33 to one of a plurality of the bit data.