An easy method for mosaicking JERS-1/SAR images was developed. According to the simulation for generating foreshortening distortion in side-lapped areas of two adjacent JERS-1/SAR images in range direction, it was proved that the differences of foreshortening distortion between the two images are decided uniquely only by surface elevation and they are not affected by the position in the side-lapped areas. It was also proved that the difference of the distortion changes in a linear relationship to the elevation value. An algorithm based on above characteristics of foreshortening distortion was tested using JERS-1/SAR images and digital elevation model with 250m grid from national digital land information and this algorithm worked well to create the mosaicked SAR image with no geometric discontinuity at the connection line of the two SAR images.