It is an object to provide a method of suitably analyzing the amount of gene expression of a single-cell.A method of detecting a nucleic acid comprising a step of sampling a single-cell from a sample containing at least a single-cell, a cell lysis step of lysing cell membrane of the sampled single-cell and extracting nucleic acids from the cell, a DNase treatment step of degrading DNA of the extracted nucleic acids with DNase, a step of hybridizing mRNA of the total RNA contained in the single-cell with oligo (dT) fixed onto a carrier, a step of performing reverse transcription of the mRNA hybridized with the oligo (dT) to fix cDNA derived from the single-cell onto the carrier, thereby preparing a single-cell derived cDNA library fixed onto a carrier, and a step of amplifying cDNA fixed onto the carrier and simultaneously detecting an amplification amount of the cDNA.