Spin-polarized scanning electron microscopy (spin-SEM) is a magnetic domain observation method. In spin-SEM, polarization of secondary electrons emitted from a sample in a scanning electron microscope is detected by a spin detector and used as a signal for forming an image. The characteristics of spin-SEM are detection of all three magnetization vector components, which leads to the detection of the magnetization vector direction, high spatial resolution of around 3 nm and applicability to samples with rough or even 3D surfaces. Spin-SEM combined with other imaging methods using an electron probe beam such as scanning Auger electron microscopy for imaging element distribution and electron backscattering diffraction microscopy for imaging crystal direction distribution provides additional information that is important to study the magnetism. Spin-SEM with these excellent characteristics has a broad range of applications from basic research to applied research and developments in various industries.