The BCS-BEC crossover in cold Fermi gases is one of the most exciting topicsin the current reaseach of physics. This phenomenon enables to study fermion superfluidity and boson superfluidity in a unified manner. Since the maximum Tc observed in the BEC regime of 6Li and 40K Fermi gases reaches about 0.2TF, we might get a hint to realize room temperature superconductivity from superfluid Fermi gases. Our group theoretically studies this exciting topic to clarify superfluid properties in the BCS-BEC crossover region.