We present the result of our preliminary FEM analysis of local deformation at Mt. Tokachi. Since 2006, displacement of several cm/yr has been observed by GPS measurement and SAR interferometry at 62-II eruptive vent which was formed by the eruptive event in 1962. The spatial scale of the deformation observed by SAR interferometry is around 2 km. This indicates that the deformation source is at the depth of less than 1 km, supporting that the deformation source is the hydrothermal activity rather than the magma chamber. As a preliminary analysis, we assumed spheroidal pressure source beneath the 62-II vent and simulated the surface deformation to observe the relation between the surface deformation and source depth/shape. We then compared the simulated deformation and SAR interferometry result to find that prolate spheroid (flattening of 0.8) at the depth of 200 m best explains the observation.