An error correcting and detecting apparatus for a CD-ROM or DVD system executes a high speed decode process. The apparatus includes an input interface, a temporary memory, a correcting circuit, a detecting circuit, a principal memory, and an output interface. The input interface fetches digital data in a block by block manner. The temporary memory stores the fetched digital data in a block by block manner. The correcting circuit performs error correction on digital data read from the temporary memory in a block by block manner using the error correction code and rewrites erroneous digital data to the temporary memory with the corrected digital data. The detecting circuit performs error detection on the error corrected digital data and supplied from the temporary memory in a block by block manner using the error detection code and sets an error flag based on a detection result. The principal memory stores, in a block by block manner, the error corrected digital data supplied to the detecting circuit from the temporary memory. The output interface transfers the error corrected digital data stored in the principal memory to an external unit.