A multistage prism window includes first and second transparent plate materials, a first prism, a reflection member, a second prism, and a heat absorption member. The first prism collects, onto the reflection member, light whose angle with respect to a normal line of the first and second transparent plate materials is equal to or greater than a first predetermined angle and transmits light whose angle with respect thereto is smaller than the first predetermined angle. The second prism collects, onto the heat absorption member, light whose angle with respect to the normal line is smaller than the first predetermined angle and equal to or greater than a second predetermined angle and transmits light whose angle with respect thereto is smaller than the second predetermined angle.