  We study even-parity black hole perturbations in Minimal Theory of Bigravity
(MTBG). We consider the Schwarzschild solution written in the spatially-flat
coordinates in the self-accelerating branch as the background solution. We
clarify the gauge transformations for the $\ell=0$, $1$, and $\geq2$ modes with
$\ell$ being the angular multipole moments under the joint foliation-preserving
diffeomorphism transformation. Requiring that the asymptotic regions in the
physical and fiducial sectors share the same Minkowski vacua, the solution to
the $\ell=0$ perturbations can be absorbed by a redefinition of the
Schwarzschild background. In order to analyze the $\ell=1$ and $\geq 2$ modes,
for simplicity we focus on the effectively massless case, where the constant
parameter measuring the ratio of the proper times between the two sectors is
set to unity and the effective mass terms in the equations of motion vanish. We
also find that as a particular solution all the $\ell=1$ perturbations vanish
by imposing their regularity at spatial infinity. For each of the $\ell\geq 2$
modes, in the effectively massless case, we highlight the existence of the
expected two propagating modes and four instantaneous modes.
