A facsimile mail box service subscriber apparatus and its operating method are disclosed by which when the facsimile message is recorded, in case of a facsimile message in ECM, it is subject to the FCS checking to store a facsimile message with no error, while, in case of a general facsimile compressed message, it is converted to a facsimile image binary data and subject to an error checking to thereby store a facsimile message without an error. Therefore, it is easy to detect an error of the facsimile data and restore it, so that a reliable facsimile service can be provided. In addition, there is an effect that the facsimile data in a binary form is stored in the storing unit, so that it can be readily adopted to an applied field such as an Internet facsimile according to a construction of its system afterwards.