In a nucleic acid isolation method for a solid biological sample, since two or more kinds of instruments are used for biological sample disruption and nucleic acid isolation, the operations are complicated, thereby increasing the operating labor, prolonging the operation time, and deteriorating the property of a nucleic acid associated with the prolonged operation time. A sample stuck to the instrument for disruption during the sample disruption operation is not brought to the subsequent nucleic acid isolation operation, thereby causing a problem of reducing the nucleic acid isolation efficiency. In the present nucleic acid isolation method, a step of disrupting a biological sample and a step of isolating a nucleic acid released from the disrupted sample are conducted with one instrument. The nucleic acid isolation efficiency can be improved without losing a sample stuck to an instrument for sample disruption, and the operability can be improved by simplifying the operations.