  The SuperFGD will be a part of the ND280 near detector of the T2K and Hyper
Kamiokande projects, that will help to reduce systematic uncertainties related
with neutrino flux and cross-section modeling. The upgraded ND280 will be able
to perform a full exclusive reconstruction of the final state from
neutrino-nucleus interactions, including measurements of low momentum protons,
pions and, for the first time, event-by event measurements of neutron
kinematics. The time resolution defines the neutron energy resolution. We
present the results of time resolution measurements made with the SuperFGD
prototype that consists of 9216 plastic scintillator cubes (cube size is 1
cm$^3$) readout with 1728 wavelength-shifting fibers going along three
orthogonal directions. We use data from the muon beam exposure at CERN. The
time resolution of 0.97 ns was obtained for one readout channel after
implementing the time calibration with a correction for the time-walk effect.
The time resolution improves with energy deposited in a scintillator cube.
Averaging two readout channels for one scintillator cube improves the time
resolution to 0.68 ns which means that signals in different channels are not
synchronous. Therefore the contribution from the time recording step of 2.5 ns
is averaged as well. Averaging time values from N channels improves the time
resolution by $\sim 1/\sqrt{N}$. Therefore a very good time resolution should
be achievable for neutrons since neutron recoils hit typically several
scintillator cubes and in addition produce larger amplitudes than muons.
Measurements performed with a laser and a wide-bandwidth oscilloscope
demonstrated that the time resolution obtained with the muon beam is not far
from its expected limit. The intrinsic time resolution of one channel is 0.67
ns for signals of 56 photo-electron typical for minimum ionizing particles.
