In this article, we have developed pressure loading technique to extend the loading density of guest alkali metals in nanoporous crystals of zeolites. Zeolite crystals have solid framework and open regular nanospace. In the nanocages of zeolite crystals, s-electrons provided by the guest alkali metals occupy quantum electronic states of clusters successively. Under the pressure by the use of the pressure medium of alkali metals, we have observed significant change in the magnetic properties, indicating that the pressure loading increases loading densities which are closely related to the s-electron occupation at the quantum states of clusters.