7. The apparatus of claim 4 , wherein the shallow parser is configured to generate corresponding trees among syntax trees including the part-of-speech sequences as a noun phrase, a compound word, an object phrase, and a subordinate clause when the calculated degrees of closeness of the part-of-speech sequences are larger than a reference value, and generate derivation trees including words constituting each part-of-speech sequence not as phrases but as independent words when the degrees of closeness are smaller than the reference value.
4. The apparatus of claim 1 , wherein the first error detector comprises: a part-of-speech sequence generation unit configured to generate the part-of-speech sequences in units of predetermined windows using the n-grams of the parts of speech tagged to the sentence; a shallow parser configured to calculate degrees of closeness of the part-of-speech sequence by parsing the part-of-speech sequences based on context free grammar (CFG) rules and regular grammar rules; and a first error detection unit configured to detect the first grammatical errors in the sentence according to the degrees of closeness calculated by the shallow parser.