A photoreceiver includes: a first light-receiving section divided into two regions by a border extending in a radial direction, and is disposed in a portion where it can receive a +1st order diffraction ray of the main beam from the polarization hologram, so as to detect a spherical aberration; a second light-receiving section is divided into two regions by a border extending in the radial direction, and is disposed in a portion where it can receive a +1st order diffraction ray of the first sub-beam from the polarization hologram, so as to detect a spherical aberration; and a third light-receiving section is divided into two regions by a border extending in the radial direction, and is disposed in a portion where it can receive a +1st order diffraction ray of the second sub-beam from the polarization hologram, so as to detect a spherical aberration. The second and third light-receiving sections are laid out such that an end of the second light-receiving section along the tangential direction and an opposite end of the third light-receiving section along the tangential direction are aligned on a straight line extending in the tangential direction across the first light-receiving section.