The present invention provides a nucleic acid collection device that can estimate the nucleic acid collection amount when collecting nucleic acids from a biological sample containing nucleic acids. The nucleic acid collection device comprises a sucking and discharging unit for sucking in and forcing out a sample containing nucleic acids, a collector for collecting the nucleic acids by sucking in and forcing out the sample using the sucking and discharging unit, a pressure measurer for measuring a discharging pressure when forcing out the sample and a sucking pressure when sucking in the sample, and measuring a differential pressure that is the difference between the discharging pressure and the sucking pressure, and an estimator for estimating the collection amount of nucleic acids collected based on the differential pressure.