In order to enable magnetic susceptibility to be measured even in a range of particle diameters smaller than by the prior art, and to measure magnetic susceptibility in the same manner also in the particle diameter range of measurement of the prior art, the present invention is provided with a first particle diameter calculation unit for calculating the particle diameter of a particle on the basis of the size of the particle in an image captured by an imaging mechanism, a second particle diameter calculation unit for calculating the particle diameter of the particle by a dynamic light scattering method or a static light scattering method on the basis of the intensity of particle-scattered light indicated by an output signal outputted from a scattered-light detector, and a magnetic susceptibility calculation unit 6 for calculating the magnetic susceptibility of the particle on the basis of a magnetophoresis speed of the particle and the particle diameter of the particle, and the present invention is configured
