  We study the statistical properties of two hard spheres in a two dimensional
rectangular box. In this system, the relation like Van der Waals equation loop
is obtained between the width of the box and the pressure working on side
walls. The auto-correlation function of each particle's position is calculated
numerically. By this calculation near the critical width, the time at which the
correlation become zero gets longer according to the increase of the height of
the box. Moreover, fast and slow relaxation processes like $\alpha$ and $\beta$
relaxations observed in supper cooled liquid are observed when the height of
the box is sufficiently large. These relaxation processes are discussed with
the probability distribution of relative position of two particles.
