An error correcting circuit includes a marker decoder for sampling 2-bit markers from a data string and, from sample values of the 2-bit markers, determine whether there is an occurrence of an error on the 2-bit markers, of an insertion error, or of a deletion error. The circuit also includes an error corrector for performing an error correction on the data string received from the marker decoder by using an error correcting code in the data string. When either one of the insertion error and the deletion error is determined to have occurred, the marker decoder can perform another error correction on the either one of the insertion error and the deletion error, and output the data string from which the 2-bit markers are removed.