From the analyses of the recent data of neutrino oscillation experiments (especially the CHOOZ and the Super KAMIOKANDE experiments), we discuss how these data affect the neutrinoless double beta decay ($(beta beta)_{0 u}$) rate and vice versa assuming that neutrinos are Majorana particles. For the case that $m_1 sim m_2 ll m_3$ ($m_i$ are neutrino masses), we obtain, from the data of the CHOOZ and Super KAMIOKANDE, $0.28 le sin^2theta_{23} le 0.76$ and $sin^2theta_{13} le 0.05$. Combining the latter constraint with the analysis of the averaged neutrino mass (< m_ u >) appeared in $(beta beta)_{0 u}$, we find that (frac{< m_ u >-m_2}{m_3-m_2}<sin^2 theta_{13} le 0.05), which leads to the constraint on (< m_ u >) as (< m_ u > le 0.05 m_3+(1-0.05)m_2). For the case that $m_1 ll m_2 sim m_3$, we find that the data of neutrino oscillation experiments and$(beta beta)_{0 u}$ imply the constraints of mixing angles.