1. An information recording method, comprising steps of: at a time of recording information: recording information to semiconductor memory in a case where an amount of free space in a recording area of the semiconductor memory equals or exceeds a first predetermined range, recording information to magnetic memory in a case where the amount of free space in the recording area of the semiconductor memory is less than the first predetermined range, and wherein an amount of free space in a recording area of the magnetic memory equals or exceeds a second predetermined range, and recording information to optical memory in a case where the amounts of free space in the recording areas of both the semiconductor memory and the magnetic memory are less than a third predetermined range; and at a time of retrieving recorded information: incrementing an access count, and moving information with a comparatively high access count to the semiconductor memory, while moving information with a comparatively low access count to the optical memory.