The museum building was originally used for adjusting the observatory's precision clocks in the early days after the Observatory was established in 1929. Several years ago it was planned that the building should be demolished since such adjustments were no longer necessary.

However, an architect pointed out the historical importance of the building itself which was one of the precious old western-style buildings constructed in the early part of the 20th century. Therefore it was repaired and developed into a Museum.

There are three rooms in the Museum, which include displays of historical astronomcal items such as a clock and solar spectrum.

1. History Room
   • History of the observatory.
   • Hyde 10cm Refractor Telescope.
   • The history of Kwasan Observatory seen in aerial photographs.
2. Astronomy and Clock Room
   • Transit by Faus.
   • The astronomical clock by Refler.
   • The master clock by Zento.
   • The cronometer by Seiko.
   • The Cook 30cm telescope, lens, and devices.
3. Solar Spectrum
   • The Heliograph by Ascania.
   • The 30cm Celostat by Club Person.
   • Old calculators.