An information storage medium and a recording/reproducing apparatus and method are provided with the ability to extend at least one middle area of an information storage medium comprising two or more recording layers so as to ensure optimal data recording/reproduction. The information storage medium comprises a plurality of recording layers, each including a user data area for recording user data and at least one middle area used by a recording/reproducing apparatus that records/reproduces data on the information storage medium to move among two recording layers, wherein the at least one middle area is extended when the information storage medium is finalized. As a result, when an information storage medium that contains an OPC area for obtaining optimum recording conditions (such as recording power) in an outer circumference thereof is finalized, and if a middle area of the disk is not large enough, the middle area can flexibly be extended.