Abstract: In a magnetooptical recording and reproducing device, a segment allocation table containing identification information for identifying whether a file should be time-continuously processed is recorded on a magnetooptical disc. When it is judged on the basis of the identification information of the table that a file to be reproduced from the magnetooptical disc of the magnetooptical recording and reproducing device is a time-continuous file, an MPU controls read-out and write-in operations for a main memory so that data contained in the file to be reproduced is written into a part of the main memory and at the same time data contained in the file to be reproduced is read out from another part of the main memory.