  We estimate the flux of the GRB neutrino background and compute the event
rate at SK and TITAND in the collapsar model, assuming that GRB formation rate
is proportional to the star formation rate. We find that the flux and the event
rate depend sensitively on the mass-accretion rate. Although the detection of
signals from GRBs seems to be difficult by SK, we find that we can detect them
by TITAND (optimistically about 20 events per year in the energy range where
the energy of anti-electron neutrino is larger than 50 MeV). Therefore, we show
that we will obtain the informations on the mass-accretion rate of collapsar by
observing the GRB neutrino background, which, in turn, should give us
informations on the total explosion energy of GRBs.
