Stress induces degeneration of brain structures and functions. Particularly, hippocampus is sensitive to stressful stimulations. In the present study, the change of synaptic related molecules in the mouse dentate gyrus was examined with immunohistochemistry after restraint stress. We subjected mice to restraint stress for 6 h per day for 4 days. As a result, the number of Ki-67, a marker for proliferation, and doublecortin (DCX), a marker for neurogenesis, immunoreactive cells was decreased in the stress group. On the other hand, the intensity of calbindinD-28k, a marker of pre-existing granule cells, immunoreactivity was increased in the granule cell layer after 4 days restraint stress. As well as, the immunoreactivity of synaptic related molecules, postsynaptic density-95 (PSD-95), growth association protein-43 (GAP-43) and beta-NADPH-d reactivity were increased in the inner molecular layer of dentate gyrus after 4 days restraint stress. In conclusion, this study shows that repeated restraint stress suppresses neurogenesis in dentate gyrus and strengthens synaptic plasticity of existing granule cells.