We measured the electrical resistivity, magnetic susceptibility, magnetization, and specific heat of the quasicrystal approximants RCd6 (R: rare earth, Y-Lu) with a body-centered cubic (bcc) crystal structure. Single crystals were grown by the Cd-self flux method and annealing method. We confirmed that the structural order-disorder transition is realized at about 160K when the lattice constant a is larger than 15.481 angstrom in YCd6, namely, for R = Pr, Nd, Sm, Gd, Tb, Dy, and Yb. At lower temperatures, RCd6 compounds, except non-4f reference compounds YCd6 and LuCd6, and a divalent compound YbCd6, are found to order antiferromagnetically. We clarified that the structural order-disorder transition has a great influence on the magnetic ordering and transport properties. The Neel temperature of RCd6 (R: Nd, Sm, Tb, and Dy) with the structural order-disorder transition is appreciably higher than the de Gennes scaling normalized by the Neel temperature of GdCd6, while the the Neel temperature of RCd6 (R: Ho, Er, and Tm) without the structural transition approximately follows the de Gennes scaling. Moreover, the electrical resistivity of RCd6 with the structural transition decreases monotonically below the Neel temperature, while it increases below the Neel temperature and a large residual resistivity remains at low temperatures in RCd6 without the structural transition. The contribution of an Einstein oscillator to the phonon specific heat is also discussed in YCd6 and LuCd6.