An electromagnetic property measuring device includes a magnetic conductive structure, a coil, and a scattering parameter measuring unit. The magnetic conductive structure includes a first side facing a sample to be tested and a second side opposite to the first side, and the first side has a magnetic gap. The coil surrounds the magnetic conductive structure to generate a magnetic field with the magnetic conductive structure. The scattering parameter measuring unit is disposed at the first side and located within a range of the magnetic field.