An observation container (10) includes: a bottom portion that includes a bottom wall (12A) (first plate part) and a bottom wall (12B) (second plate part) which intersect each other and that is configured to accommodate a liquid sample O as a sample containing microparticles to be imaged by imaging units (30A) and (30B) serving as an imaging device; and a region that has transparency with respect to a wavelength of light used for observation of the microparticles.