A stirring device (1) causes stirring blades (30) in a processing tank (2) to rotate on a stirring shaft (37) to stir a material to be stirred. A lid (5) is provided to an upper opening of the processing tank (2) so as to be capable of being detached therefrom. When a lid-detection means (6) detects that the lid (5) is closed, a controller causes the stirring shaft (37) to rotate if a stirring start switch (51) is operated, and, when the lid-detecting means (6) does not detect that the lid (5) is closed, the controller does not cause the stirring shaft (37) to rotate even if the stirring start switch (51) is operated, but does cause the stirring shaft (37) to rotate only when predetermined switches (53, 54) are operated. It is preferable that the predetermined switches be configured as two switches (53, 54) arranged and separated by a distance at which operation using one hand is impossible.