We present the results of deep NIR photometric surveys with UKIRT and Subaru telescope searching for young brown dwarfs and planetary-mass objects in Serpens Cluster A/B/South and subsequent NIR spectroscopy with Subaru. The spectroscopic temperature for newly identified objects, together with the bolometric luminosity, indicate that they could be young brown dwarfs and isolated planetary-mass objects. All the derived mass function appears to be flat toward the planetary-mass regime, but their slope slightly changes depending on the cloud environments.