Abstract: Provided is a small-sized quantitative phase measurement apparatus. The quantitative phase measurement apparatus 1 includes a reflective polarization splitting element 17. The reflective polarization splitting element 17 is disposed at a focusing position of the converging light L4, and performs splitting of the converging light L4 into two polarized beams having different polarization directions and reflection of the two polarized beams to form a first polarized beam L5 and a second polarized beam L6 both travelling toward the converging optical system 16.