  We report the novel pressure(P)-temperature(T) phase diagrams of
antiferromagnetism (AF) and superconductivity (SC) in CeRhIn$_5$, CeIn$_3$ and
CeCu$_2$Si$_2$ revealed by the NQR measurement. In the itinerant helical magnet
CeRhIn$_5$, we found that the N\'eel temperature $T_N$ is reduced at $P \geq$
1.23 GPa with an emergent pseudogap behavior. The coexistence of AF and SC is
found in a narrow P range of 1.63 - 1.75 GPa, followed by the onset of SC with
line-node gap over a wide P window 2.1 - 5 GPa. In CeIn$_3$, the localized
magnetic character is robust against the application of pressure up to $P \sim$
1.9 GPa, beyond which the system evolves into an itinerant regime in which the
resistive superconducting phase emerges. We discuss the relationship between
the phase diagram and the magnetic fluctuations. In CeCu$_2$Si$_2$, the SC and
AF coexist on a microscopic level once its lattice parameter is expanded. We
remark that the underlying marginal antiferromagnetic state is due to
collective magnetic excitations in the superconducting state in CeCu$_2$Si$_2$.
An interplay between AF and SC is discussed on the SO(5) scenario that unifies
AF and SC. We suggest that the SC and AF in CeCu$_2$Si$_2$ have a common
mechanism.
