  The $D=4$ supersymmetric Yang-Mills quantum mechanics with $SU(2)$ and
$SU(3)$ gauge symmetry groups is studied. A numerical method to find finite
matrix representation of the Hamiltonian is presented in detail. It is used to
find spectrum of the theory. In the $SU(2)$ case there are bound states in all
channels with definite total number of fermions and angular momentum. For 2,3,4
fermions continuous and discrete spectra coexist in the same range of energies.
These results are confirmation of earlier studies. With $SU(3)$ gauge group,
the continuous spectrum is moved to sectors with more fermions. Supersymmetry
generators are used to identify supermultiplets and determine the level of
restoration of supersymmetry for a finite cutoff. For both theories, with
$SU(2)$ and $SU(3)$ symmetry, wavefunctions are studied and different behavior
of bound and scattering states is observed.
