Is CP Violation Observable in Long Baseline Neutrino Oscillation Experiments?

We have studied the direct measurements of $CP$ violation in the neutrino oscillations: the difference of the transition probabilities between $CP$-conjugate channels in the long baseline accelerator experiments. In those experiments, the $CP$ violating effect is not suppressed if the highest neutrino mass scale is taken to be $1\sim 10 \eV$, which is appropriate for the cosmological hot dark matter. The upper bounds of $CP$ violation have been caluculated for three cases, in which mixings are constrained by the recent short baseline ones. The caluculated upper bounds are larger than $10^{-2}$, which will be observable in the long baseline accelerator experiments. The new reactor disappearance experiments will provide severer bounds of $CP$ violation in the near future.\par