Existence of bosons with strangeness zero besides pion is expected in the full symmetry theory of the Sakata model and ρ-, ω-,… mesons have been recently found. It is investigated whether these bosons could explain the nuclear forces, especially, the spin-orbit coupling interaction. Two cases are discussed: One is to identify the phenomenological potential with a sum of one-boson-exchange-potentials, and the other is to explain the phenomenological potential by the one-pion-exchange-potential, two-pion-exchange-potential, together with a sum of one-boson-exchange-potentials. The analyses show that the presence of an I = 1 vector boson (mainly interacting through tensor coupling) and an I = 0 vector boson (mainly interacting through vector coupling) for both cases. They may be identified as the ρ-and ω-meson respectively. In addition, an I = 0 scalar boson is needed for the first case, and an I = 0, scalar or pseudoscalar boson is required for the second case. (Existence of other bosons is not necessarily excluded.) Consistency of the obtained results with other experimental evidence and with the mass level scheme of the Sakata model is discussed.