  We report the results of the angular-dependent magnetoresistance oscillations
(AMROs), which can determine the shape of bulk Fermi surfaces in
quasi-two-dimensional (Q2D) systems, in a highly hole-doped Fe-based
superconductor KFe$_2$As$_2$ with $T_c \approx$ 3.7 K. From the AMROs, we
determined the two Q2D FSs with rounded-square cross sections, corresponding to
12% and 17% of the first Brillouin zone. The rounded-squared shape of the FS
cross section is also confirmed by the analyses of the interlayer transport
under in-plane fields. From the obtained FS shape, we infer the character of
the 3d orbitals that contribute to the FSs.
