A processing apparatus includes: a light source unit configured to emit partially coherent light having a coherence length that is equal to or more than inverse of a scattering coefficient of a light scattering body and shorter than half of inverse of a reduced scattering coefficient of the light scattering body an illumination unit configured to irradiate an illumination area on a surface of the light scattering body, with the partially coherent light emitted from the light source unit a detection unit configured to detect, in a detection area including the illumination area, a signal of scattered and returned light from the light scattering body and an interference component extracting unit configured to extract an interference component by excluding a noninterference component from the signal of the scattered and returned light detected by the detection unit.
