This invention provides a sample analyzing device and sample analyzing method designed to suppress nonuniform capture of magnetic particles (10) and detect a desired substance with higher accuracy. The sample analyzing device includes a flow channel (15) that conducts thereinto a sample which contains the magnetic particles (10), and magnetic field generating means (12) that generates magnetic fields for capturing the magnetic particles (10) in a magnetic particles capturing region of the flow channel (15); wherein the flow channel has at least one of structural characteristics that a cross-sectional area of the flow channel, at a downstream end of the magnetic particles capturing region, is larger than a cross-sectional area of the flow channel, at an upstream end of the magnetic particles capturing region, and that the magnetic fields generated by the magnetic field generating means (12) have a greater magnitude at a downstream side of the magnetic particles capturing region than at an upstream side thereof.