JERS-1 SAR interferometry is applied to Kirishima volcanic complex, and we detected the ground deformation associated with the subsidence at the summit of Iwo-yama. The mean deformation rate for the analyzed three pairs of data was apparently constant for about 3.4 years. By inverting the obtained line-of-sight displacement field for each pair of data, we estimate the parameters of pressure source by using the Mogi model. Estimated depth of the source is about 270m, which is consistent with the depth of aquifer suggested from MT survey. Hence, this subsidence could be caused by the volume change of the aquifer system beneath the Iwo-yama. The rate of volume change was about -1.3q104 m3/yr. Keywords: Kirishima, deformation, SAR, interferometry, aquifer