Currently, Super-K experiment uses Geant3 based simulation software
(SKDETSIM), and the new phase of the experiment, which is called "SK-Gd Project" will start soon.
Main purpose of the SK-Gd is the first discovery of the Diffuse Supernova Neutrino Background, which is neutrinos generated from the past Supernova explosion.
In SK-Gd, precise understanding about neutron capture of Gadolinium is crucial.
In order to apply the latest interaction model based on the new experimental results, Geant4 based Super-K simulation software "SKG4" is now on developing.
In this article, The current development status of SKG4, and some results of comparison with SKDETSIM are presented.