A database management device includes: plural index blocks that have an index entry and an access counter including a read counter and a write counter; an access management unit that updates the read counter in response to a read access to an index block and updates the write counter in response to an update access to the index block; an extended block manipulation unit that acquires an extended block not identified with an index entry of another index block and serving as a destination of storing a new index entry on the basis of a result of comparison between the read counter and the write counter of a leaf block serving as a target of inserting the new index entry, and sets identification information for identifying the extended block to the leaf block serving as the target of insertion.