8. The apparatus of claim 1 , wherein the second error detection unit comprising: an n-gram generation unit configured to generate the morpheme sequences by binding the morphemes in the preset window size in one or more directions of a forward direction and a backward direction; a search unit configured to search whether or not the morpheme sequences identical to the generated morpheme sequences are in the example-based index DB; a suitability calculation unit configured to extract the frequencies of appearance of the morpheme sequences identical to the generated morpheme sequences and calculate respective suitability scores of the morpheme sequences based on the extracted frequencies of appearance; and an error determination unit configured to detect second grammatical errors by determining whether the suitability scores are smaller than a threshold or whether the suitability scores are changed larger than a predetermined value.
8. The apparatus of claim 1 , wherein the second error detection unit comprising: an n-gram generation unit configured to generate the morpheme sequences by binding the morphemes in the preset window size in one or more directions of a forward direction and a backward direction; a search unit configured to search whether or not the morpheme sequences identical to the generated morpheme sequences are in the example-based index DB; a suitability calculation unit configured to extract the frequencies of appearance of the morpheme sequences identical to the generated morpheme sequences and calculate respective suitability scores of the morpheme sequences based on the extracted frequencies of appearance; and an error determination unit configured to detect second grammatical errors by determining whether the suitability scores are smaller than a threshold or whether the suitability scores are changed larger than a predetermined value. 9. The apparatus of claim 8 , wherein the n-gram generation unit is configured to separately generate a forward morpheme sequence by binding the morphemes arranged in the forward direction in the preset window size and a backward morpheme sequence by binding the morphemes arranged in the backward direction in the preset window size.