A method for synthesizing cDNA characterized by preparing a reaction solution that does not allow an endodeoxyribonuclease to show its activity, without thermal deactivation of the endodeoxyribonuclease or removal of the endodeoxyribonuclease, and carrying out a reverse transcription reaction, wherein the reaction solution contains a treated sample and a reverse transcriptase, the treated sample being formed by treating a sample comprising RNA and DNA with the endodeoxyribonuclease to degrade DNA in the sample. The method and the kit for synthesizing cDNA of the present invention are widely useful in genetic engineering fields.