An analysis device comprising: a turntable holding a specimen analysis disc having a reaction region on which nanoparticles binding to substances to be detected are captured; a turntable drive unit configured to rotate the turntable; a turntable drive circuit configured to control the turntable drive unit; a reference position detection sensor configured to detect a reference position of the specimen analysis disc; an optical pickup driven in a direction perpendicular to a rotation axis of the turntable, and configured to emit laser light to the reaction region, to receive a reflected light from the reaction region, and to generate a light reception level signal; an optical pickup drive circuit configured to control an operation of the optical pickup; a storage unit storing a measurement parameter (SPiw), the measurement parameter (SPiw) including a predetermined time (TDiw) and timing information for generating measurement gate signals, the predetermined time (TDiw) being determined in accordance with a positional relationship between a tolerance region which includes the reaction region and the reference position, and a velocity of rotation of the specimen analysis disc; and a controller configured to control the turntable drive circuit and the optical pickup drive circuit, wherein the controller is configured to sequentially generate a plurality of measurement gate signals having a predetermined pulse width (Tp) while the optical pickup emits laser light to the tolerance region, from a time when the predetermined time (TDiw) included in the measurement parameter (SPiw) has elapsed since the reference position detection sensor detects the reference position, count the number of the nanoparticles of each of the measurement gate signals based on the light reception level signal, calculate a passed length (Liw) of the reaction region according to a measurement result per measurement gate signal, specify a measurement gate section (Tiwa) in the reaction region according to the passed length (Liw), and add up the number of the nanoparticles of the respective measurement gate signals in the measurement gate section (Tiwa) to count the number of the nanoparticles captured on the reaction region. a turntable holding a specimen analysis disc having a reaction region on which nanoparticles binding to substances to be detected are captured; a turntable drive unit configured to rotate the turntable; a turntable drive circuit configured to control the turntable drive unit; a reference position detection sensor configured to detect a reference position of the specimen analysis disc; an optical pickup driven in a direction perpendicular to a rotation axis of the turntable, and configured to emit laser light to the reaction region, to receive a reflected light from the reaction region, and to generate a light reception level signal; an optical pickup drive circuit configured to control an operation of the optical pickup; a storage unit storing a measurement parameter (SPiw), the measurement parameter (SPiw) including a predetermined time (TDiw) and timing information for generating measurement gate signals, the predetermined time (TDiw) being determined in accordance with a positional relationship between a tolerance region which includes the reaction region and the reference position, and a velocity of rotation of the specimen analysis disc; and a controller configured to control the turntable drive circuit and the optical pickup drive circuit, wherein the controller is configured to sequentially generate a plurality of measurement gate signals having a predetermined pulse width (Tp) while the optical pickup emits laser light to the tolerance region, from a time when the predetermined time (TDiw) included in the measurement parameter (SPiw) has elapsed since the reference position detection sensor detects the reference position, count the number of the nanoparticles of each of the measurement gate signals based on the light reception level signal, calculate a passed length (Liw) of the reaction region according to a measurement result per measurement gate signal, specify a measurement gate section (Tiwa) in the reaction region according to the passed length (Liw), and add up the number of the nanoparticles of the respective measurement gate signals in the measurement gate section (Tiwa) to count the number of the nanoparticles captured on the reaction region.