A portable body fat measurement device, method and medium that can accurately measure body fat by using a small optical sensor having a comparatively small cross-section. The device includes a light source unit having at least two side-view light sources and a light guiding efficiency optical element to guide an optical signal generated from the at least two side-view light sources to a measuring point, an optical detection unit to detect a scattered optical signal, generated by a scattering of the optical signal irradiated to the measuring point, and to transform the scattered optical signal into an electrical signal; and an electrical signal calculation unit to calculate body fat information based on the electrical signal.