  Motivated by the recent experimental observations of quantum oscillations in
the Kondo insulators SmB$_6$ and YbB$_{12}$, we study magneto-optical
conductivity of Kondo insulators. We show that there exist non-trivial
cyclotron resonance peaks in a frequency domain below the hybridization gap as
a result of the characteristic Landau level structure of the system.
Furthermore, these low energy peaks are enhanced near the insulator-metal phase
transition driven by an applied magnetic field and stable even at low
temperatures. They are smoothly connected via Kondo effect to resonance peaks
for unhybridized conduction and $f$-electrons at high temperature. The
non-trivial cyclotron resonance is a dynamical counterpart of quantum
oscillations in static quantities, and through this intimate connection it will
provide a useful insight for the latter.
