For high data rate and long-distance communication of satellite, a large aperture antenna on satellite is required. However, it is difficult to make high flatness surface in space and the current study on large antennas for satellites assumes the high flatness structures. In this study, to construct the reflectarray antenna on the deployable membrane structure, we propose the active reflectarray which actively adjusts the reflection phase of elements by varactor diodes and compensate the low flatness surface. We analyze the nonflat reflectarray and confirm our proposed method.