This paper presents an online method for localizing the positions of multiple sound sources and stationary robots and synchronizing microphone arrays attached to those robots. Since each robot can estimate only the directions of sound sources, the two-dimensional source positions can be estimated from the source direction estimated by each robot using a triangulation. In addition, mixture signals can be separated accurately by regarding multiple microphone arrays as one big array. To perform these tasks, some methods have been proposed for localizing and synchronizing microphone arrays. These methods, however, assume only a single sound source exists. To overcome this limitation, we estimate the directions of arrival (DOAs) and separate observed signals to estimate the time differences of arrival (TDOAs) by using microphone array techniques, and integrate the DOAs and TDOAs by using a state-space model. The latent variables are estimated in an online manner with a FastSLAM2.0 algorithm.