The Josephson effect is one manifestation of the quantum aspect of macrosco
pic objects. It has been tested in various macroscopic systems to confirm t
heir quantum-mechanical nature. In some of the systems, the total number of
particles in the system is fixed. In such a case, the dynamics of the syst
em is restricted and hence a new dynamical state might be expected to appea
r. In this paper, we discuss the Josephson effect under a particle-number r
estriction, and explore the new dynamical state that emerges from the restr
iction. We also discuss macroscopic quantum tunneling from the state.