This invention provides an image capturing apparatus which sets the spectral characteristics of a split light beam to be substantially equal to those of straight traveling light upon splitting a light beam coming from a photographing optical system and enables an autofocus detection function by the split light with a sufficient light amount. A digital camera includes a photographing optical system, beam splitter, focus detection sensor, polarizing filter, and CMOS sensor. The beam splitter splits a light beam which travels toward the CMOS sensor that receives an object image formed by the photographing optical system, depending on the direction of polarization, and the focus detection sensor performs focus detection based on the light beam split by the beam splitter. The polarizing filter removes substantially the same polarized light component as a polarized light component that travels toward the focus detection sensor as a result of splitting by the beam splitter.