1. A storage device comprising: an interface connected to a host system and configured to receive a request from the host system; a first memory block configured to store inverted files that are created for each content, the inverted files storing IDs of files including each content; a second memory block configured to store a file search table; and a controller configured to control information transmission and reception with the interface, reading and writing to the first memory block, and reading and writing to the second memory block, without an external bus, wherein the controller conducts a search by: upon receiving a file write request via the interface, stores file IDs that are designated by the file write request in the inverted files corresponding to a content included in a file that is designated by the file write request, upon receiving a content search request via the interface, stores, in the file search table, the file IDs stored in the inverted files that are identified based on the content designated by the content search request, outputs the file IDs stored in the file search table from the interface as a search result for the content search request; wherein upon receiving a Boolean operation request for the content search results corresponding to first and second contents via the interface, the controller stores, in the file search table, a list of file IDs stored in the inverted files corresponding to the first content, and rewrites the list of file IDs in the file search table in accordance with a Boolean operator for each file ID stored in the inverted files corresponding to the second content, and outputs the list of file IDs stored in the file search table from the interface.