Provided are: a reverse transcriptase mutant including an amino acid mutation at a position corresponding to position 55 of the amino acid sequence of wild-type reverse transcriptase derived from the Moloney murine leukemia virus, wherein the reverse transcriptase mutant is characterized in that the amino acid mutation is a substitution from threonine to another amino acid, and the other amino acid is selected from the group consisting of amino acids having a nonpolar aliphatic side chain and amino acids having a polar acidic functional group side chain; a nucleic acid that encodes the mutant; a method for producing the mutant and the nucleic acid that encodes the mutant; a method for synthesizing cDNA in which the mutant is used; and a composition and kit including the mutant.