We investingate the phase structure of the Su(3) lattice gauge system coupled with a scalar field on the basis of the lowest-order mean field approximation. Two cases are considered for the SU(3) representation of the scalar field. For the fundamental representation, the resultant phase diagram is shown to agree qualitatively with the Monte Carlo results, if we take into account the analyses made in the limiting cases for the parameters of the system. For the adjoint one, however, the transition caused by the gauge fields of the residual subgroup SU(2)×U(1) does not appear due to the too simple form wr assume for the mean gauge-field.

J. Sci. Hiroshima Univ., Ser. A, Vol.49, (1985), No.3