A stirring device 100 comprises a chamber 101, and a stirrer 102 for stirring molten glass 7 in the chamber 101. The stirrer 102 has a shaft 105 as a rotation axis, and blades 106a-106e disposed in a plurality of tiers on a side wall of the shaft 105. The blades 106a-106e have support plates 108 and ancillary plates 109. The ancillary plates 109 create, in the molten glass 7, a flow in the radial direction of the shaft 105.