An apparatus for supplying insulating liquid for forming an insulation coating layer on an electrode, the apparatus comprising: a storage tank where the insulating liquid is stored; a coating die where the insulating liquid is coated on an electrode; a supply line which connects the storage tank to the coating die and supplies the insulating liquid to the coating die; a pump which is installed on the supply line; an airtight defoaming tank which is connected to the storage tank by a pipe and supplies defoamed insulating liquid to the storage tank, the defoaming tank also connected to a vacuum pump by a connection line and to a discharge line to discharge air from the defoaming tank; wherein a predetermined stirring member comprising stirring blades is installed at the defoaming tank; a vacuum pump which defoams bubbles of the insulating liquid in the defoaming tank by applying vacuum to the defoaming tank; at least one bubble sensor (190,190') which is installed on the supply line and senses generation of bubbles in the supply line in real time; and a controller for: - supplying the insulating liquid to the coating die if the amount of bubbles sensed by the bubble sensor (190, 190') is equal to or less than a predetermined value and stopping the supply of the insulating liquid to the coating die if the amount of bubbles sensed by the bubble sensor (190, 190') exceeds the predetermined value; or - adjusting a vacuum degree of the vacuum pump according to the amount of bubbles sensed by the bubble sensor (190, 190'); or - adjusting a number of rotations of stirring blades installed at the defoaming tank according to the amount of bubbles sensed by the bubble sensor (190, 190'). a storage tank where the insulating liquid is stored; a coating die where the insulating liquid is coated on an electrode; a supply line which connects the storage tank to the coating die and supplies the insulating liquid to the coating die; a pump which is installed on the supply line; an airtight defoaming tank which is connected to the storage tank by a pipe and supplies defoamed insulating liquid to the storage tank, the defoaming tank also connected to a vacuum pump by a connection line and to a discharge line to discharge air from the defoaming tank; wherein a predetermined stirring member comprising stirring blades is installed at the defoaming tank; a vacuum pump which defoams bubbles of the insulating liquid in the defoaming tank by applying vacuum to the defoaming tank; at least one bubble sensor (190,190') which is installed on the supply line and senses generation of bubbles in the supply line in real time; and a controller for: - supplying the insulating liquid to the coating die if the amount of bubbles sensed by the bubble sensor (190, 190') is equal to or less than a predetermined value and stopping the supply of the insulating liquid to the coating die if the amount of bubbles sensed by the bubble sensor (190, 190') exceeds the predetermined value; or - adjusting a vacuum degree of the vacuum pump according to the amount of bubbles sensed by the bubble sensor (190, 190'); or - adjusting a number of rotations of stirring blades installed at the defoaming tank according to the amount of bubbles sensed by the bubble sensor (190, 190'). - supplying the insulating liquid to the coating die if the amount of bubbles sensed by the bubble sensor (190, 190') is equal to or less than a predetermined value and stopping the supply of the insulating liquid to the coating die if the amount of bubbles sensed by the bubble sensor (190, 190') exceeds the predetermined value; or - adjusting a vacuum degree of the vacuum pump according to the amount of bubbles sensed by the bubble sensor (190, 190'); or - adjusting a number of rotations of stirring blades installed at the defoaming tank according to the amount of bubbles sensed by the bubble sensor (190, 190').