To provide a circulating defoaming device high in coating work efficiency without bringing even minute air bubbles to a coating surface in a coating process.

This device is a defoaming tank 2 having a thin film forming deforming plate 50 inside thereof which has a fixed width and is provided with liquid dripping preventive guides at the both ends in order to remove minute air bubbles contained in a coating liquid. The thin film forming defoaming plate 50 is inclined at an inclined angle θ and the thin film forming defoaming plate 50 is arranged din a spiral along an inner wall 2a of the defoaming tank 2 or the plural thin film forming defoaming plates 50 are arranged in an alcove shelves structure on an opposite surface to one surface of the inner wall 2a of the defoaming tank 2. Moreover, an upper feeding part 40 for feeding a circulating coating liquid B to the thin film forming deforming plate 50 is made to a slit-shaped state.