There is provided a nucleic acid extraction method applicable to microbes in a relatively wide range, and capable of rapidly extracting nucleic acid. The nucleic acid extraction method comprises the steps of introducing a cell suspension into a vessel, sealing the vessel, and preheating a heater up to a set temperature not lower than 100° C. Further, the method comprises the step of bringing the vessel into contact with the heater heated up to the set temperature, thereby heating the cell suspension housed in the vessel up to a prescribed highest temperature at not lower than 100° C. with the vessel held in a sealed state.