To solve the problem that it is difficult to use one warning device for multiple purposes and utilization efficiency is low when an extension body is fixedly attached on a base.

A blower 5 for feeding the air from a large-sized air inlet 2 and a light emitting device 6 for radiating light from the air inlet 2 to the outside are stored inside a box-like base 1 on which the air inlet 2 is opened. An intake port 12 matching to the air inlet 2 and for sucking the air inside is opened to an extension body 11, the extension body 11 expands by supply of the air inside through the air inlet 2 and contracts by discharge of the air inside. The extension body 11 is attachably/detachably attached to the base 1.