To provide: (1) a modified release liquid (suspension) containing mirabegron, (2) a ready-to-suspend pharmaceutical composition containing mirabegron, and (3) a mirabegron-containing pharmaceutical composition that does not generate undissolved lumps, even when it is suspended at the time of use. The present invention relates to a pharmaceutical composition containing a complex of mirabegron or a pharmaceutically acceptable salt thereof with sodium polystyrene sulfonate.
