An error correcting controller for connecting an old host controller having an old error correcting function with a new flash memory which requires a new error correcting function is provided. When the old host controller needs to write data into the new flash memory, the error correcting controller generates a new error correcting code according to the new error correcting function for the data. Then, when the old host controller needs to read the data from the new flash memory, the error correcting controller performs an error correcting procedure according to the new error correcting code and transmits information to the old host controller according to the result of the error correcting procedure and the old error correcting function. Accordingly, it is possible to allow the old host controller to access the new flash memory without changing the architecture of the old host controller.