For optimization and accurate prediction of the amount of H- ion production in negative ion sources, analysis of electron energy distribution function (EEDF) is necessary. We are developing a numerical code which analyzes EEDF in tandem-type arc-discharge sources. It is a three-dimensional Monte Carlo simulation code with the realistic geometry and magnetic configuration. Coulomb collision between electrons is treated with "Binary Collision" model and collisions with hydrogen species are treated with "Null-collision (NC)" method. We have applied this code to the analysis of the JAEA 10 ampere negative ion source. The numerical result shows that the obtained EEDFs reasonably agree with experimental results.