To provide a holder for a flat recording medium with which a malfunction such as a failure in reading data is prevented even if the holder has been stored for a long time in such a state that it is interfiled or inserted into a book.

The holder 10 is formed like a bag comprising two sheetlike base materials 11 and 12 glued to each other with a storage space of a flat recording medium 20 provided. A cutting line as an insert port for the medium is formed, and also a breakable part for forming a take-out port is formed. The medium 20 is received from the cutting line on a rear. Even if an adhesive of a seal for sealing the cutting line alters in quality after a long period of time, the medium inside is taken out not from the cutting line but with perforations 14 as the breakable part broken. Therefore, it is not necessary to peel off the seal for unsealing, so that a data surface of the recording medium 20 is not contaminated with the adhesive of the seal as in a conventional one.