A nucleic acid extracting device includes an upper module, a lower module, and a material for capturing nucleic acid. The lower module has a sample reservoir receiving a sample, an elution reservoir receiving an elution, and a nucleic acid capturing chamber with the material disposed therein. The upper module has a sample channel that communicates with the sample reservoir, and an elution channel that communicates with the elution reservoir. The nucleic acid capturing chamber communicates with the sample channel and the elution channel. When a sample enters the nucleic acid capturing chamber via the sample channel, a nucleic acid in the sample is absorbed by the material in the nucleic acid capturing chamber, and the elution enters the nucleic acid capturing chamber, via the elution channel, to wash the nucleic acid out of the nucleic acid capturing chamber.