An object of the present invention is to provide a sustained release composition containing SDF-1. The present invention provides a sustained release composition containing (1) SDF-1 and (2) a hydrogel containing modified gelatin having a carboxyl group and/or a sulfo group. Since the composition can release SDF-1, a chemokine which is a capable of promoting accumulation of vascular progenitor cells in vivo, in the sustained manner, it can be useful for treatment and/or suppression of symptom progression of ischemic disease or bone disease, as pharmaceutical preparations in various formulations.