To obtain a coaster capable of surely supporting dew condensation water dew-condensed on a glass, eliminating the need of consciously returning the glass onto the coaster, and preventing articles on a table and clothes from getting wet even when the glass is lifted.

The coaster comprises a coaster body capable of supporting the dew condensation water of the glass, and an attaching/detaching mechanism capable of freely detachably locking the glass attached to the coaster body.