Tc oscillation phenomenon of Nb/Co and V/Co superconductor/ferromagnet multilayers has been observed as a function of Co layer thickness dCo. Spontaneous magnetization appeared for dCo≳7 A in both Nb/Co and V/Co systems. Tc exhibited double minimum oscillations with the first local minimum at ∼12 A for Nb/Co and at ∼18 A for V/Co and with the second local minimum at ∼32 A for both systems. The first minimum may be caused by a combined effect of magnetic spin-flip scattering, resonance scattering by Co virtual levels in the interfacial region and thickness dependent exchange field. The second minimum is found to be consistent with the appearance of so-called π-phase.