We analyze Hamiltonian equivalence between Jordan and Einstein frames considering a minisuperspace model of flat Friedmann-Lemaître-Robertson-Walker (FLRW) Universe in Brans-Dicke theory. Hamiltonian equations of motion are derived in the Jordan, Einstein, and in the antigravity (or anti-Newtonian) frames. We show that applying the Weyl (conformal) transformations to the equations of motion in the Einstein frame we did not get the equations of motion in the Jordan frame. Vice-versa, we re-obtain the equations of motion in the Jordan frame applying the anti-gravity inverse transformation to the equation of motion in the anti-gravity frame.I.