The invention open as the stability of the reverse transcriptase is increased, more specifically to SEQ ID NO: M-MLV 63 th glutamine derived from the amino acid sequence of the reverse transcriptase described in 1 (Q63), the 264th lysine (K264), the group consisting of the 295th lysine (K295), 306 th threonine (T306), 346-th glutamic acid (E346), 408 th proline (P408), 438 th histidine (H438), and 454 th asparagine (N454) at least one amino acid is selected from optionally substituted with other amino acids relates to a mutant reverse transcriptase of the thermal stability increased. Since the mutant reverse transcriptase of the present invention exhibit excellent heat stability as compared to wild-type reverse transcriptase, even if efficient unable to obtain a reverse transcription product as due to structural interference of a specific RNA that can form a stable secondary structure in the high-temperature stable reverse transcriptase It has the advantage that the activity can be expressed to achieve the desired cDNA.