<p>An electrophoretic device includes a transparent substrate (10) in which a flow path (12) for electrophoretic migration is provided, a detection optics system (30) which irradiates an excitation light onto the substrate (10) to detect a detection light excited by the excitation light, a movement unit (24) to move at least one of the substrate (10) and the detection optics system (30) in the direction perpendicular to the extending direction of the flow path (12), and a control unit (40) which determines an end position of the flow path (12) depending on a change in intensity of the detection light detected in association with movement to align the excitation light with the flow path (12).</p>
