A magnetic information processing apparatus for registering transaction information on a line in a document and storing the location of the line in magnetic media attached to the document, includes a magnetic head, a document receptacle configured to receive the document on which the magnetic media storing the position where the immediately previous transaction information is registered is attached, and a processing unit. The processing unit is programmed to control the magnetic head to read information from a first position of the magnetic media, move to a second position of the magnetic media, and read additional information from the second position of the magnetic media, extract registration position information indicating the location of the most recent previous registration position from the result of reading of the first and second positions of the magnetic media by the magnetic head, and output the extracted registration position information.