Energy-independent hyperon-nucleon ( YN) effective interactions are derived from the Jülich JA and JB meson-exchange potentials. A folded-diagram method is employed, where the effective interaction Veff is given as a Q̂- box folded-diagram series. A model space consisted of nucleons in the 0 p1 s0 d shells and hyperons in the 0 s0 p shells is employed. We first derive the YNG-matrix corresponding to this model space, with an accurate treatment of the Pauli exclusion operator for the G-matrix. Then the Q̂- box is evaluated including diagrams first- and second-order in G. A non-degenerate Lee-Suzuki iteration method is employed to sum up the folded-diagram series. We have applied our derived Veff to Λ18O, and have found that the effects of core polarization and folded diagrams are both important for the YNVeff.