Provided are a holographic information recording/reproducing apparatus in which positions of books can be accurately ascertained in a holographic recording medium, and a method for seeking books in the same. The apparatus includes an aperture plate disposed in an optical path of a signal beam reproduced from a reference beam that is incident on a holographic recording medium, and having an opening for restricting a width of the signal beam; one or more photodetectors installed on a surface of the aperture plate along a circumference of the opening; and a book position calculator to calculate positions of one or more books from the output of the photodetectors, wherein a cross-section of the reference beam incident on the holographic recording medium is larger than the size of the one or more books.