There is provided is a nucleotide primer set for LAMP amplification used for detecting genotypes of single-nucleotide polymorphisms C677T and A1298C of an MTHFR gene. There is also provided a nucleotide probe for detecting an amplification product amplified by the primer set according to the present invention. There is also provided a method of detecting the genotypes of the single-nucleotide polymorphisms C677T and A1298C in the MTHFR gene, by using the primer set according to the present invention.