This paper discusses the surface ordering and the adsorption phenomena of solutions of rigid-rod-like molecules. Here we focus on the planar adsorption of the rigid-rod-like molecules. We find that, for the attractive wall which preferentially adsorbs the rodlike molecules, the surface phase has two phase transitions when the bulk concentration is increased : One transition occurs when the adsorption amount jumps at a concentration phi(c) where the surface phase changes from an isotropic to a nematic state while the bulk is still in an isotropic state. The other occurs when the adsorption isotherms have a kink at the bulk critical concentration phi(IN) where the bulk phase changes from an isotropic to a nematic state. For the hulk concentration phi(c) < phi < phi(IN), we find the wetting of an isotropic bulk phase with a nematic surface phase. When phi < phi(c) (phi > phi(IN)), both bulk and the surface phases are in isotropic (nematic) states. For various values of the axial ratio of the rigid-rod-like molecules and adsorption energy, we examine the adsorption isotherms, the surface tensions, and the surface phase transitions. We also discuss the surface transitions on repulsive walls.