  We study visible neutrino decay at the reactor neutrino experiments KamLAND
and, JUNO. Assuming the Majoron model of neutrino decay, we obtain constraints
on the couplings between Majoron and neutrino as well as on the lifetime/mass
of the most massive neutrino state i.e., $\tau_{3} / m_{3}$ or $\tau_{2} /
m_{2}$, respectively, for the normal or the inverted mass orderings. We obtain
the constraints on the lifetime $\tau_{2} / m_{2} \geq 1.4 \times
10^{-9}~\rm{s/eV}$ in the inverted mass ordering for both KamLAND and JUNO at
90% CL. In the normal ordering in which the bound can be obtained for JUNO
only, the constraint is milder than the inverted ordering case, $\tau_{3} /
m_{3} \geq 1.0 \times 10^{-10}~\rm{s/eV}$ at 90% CL. We find that the
dependence of lightest neutrino mass ($=m_{\rm{lightest}}$), $m_1 (m_3)$ for
the normal (inverted) mass ordering, on the constraints for the different types
of couplings (scalar or pseudo-scalar) is rather strong, but the
$m_{\rm{lightest}}$ dependence on the lifetime/mass bound is only modest.
