Development of an accelerator-driven compact neutron source for BNCT, Boron Neutron Capture Therapy, has started in Nagoya University. We will show the results of improved design around the neutron beam exit of the Beam Shaping Assembly. We proposed a use of an “Extension collimator” that can make it easier to set a patient in a comfortable position during the neutron irradiation. Additionally, we could greatly improve performance of the collimator by using a new nozzle structure called as “Ni implant nozzle”. We, consequently, achieved the neutron beam characteristics that almost satisfied all of the recommended values reported in IAEA-TECDOC-1223.