A fixing device for fixing an image comprising a liquid developer on a recording material includes a feeding belt for feeding the recording material; a plurality of air vents, provided in a region of the feeding belt on which the recording material is fed, for sucking the recording material onto the feeding belt; a fan for sucking the recording material toward the feeding belt; and a heating source for heating the image on the recording material fed by the feeding belt, by radiant heat, and satisfies the following equation: db·Φb·K