A liquid treatment apparatus, comprising: a tank; a liquid supply pump configured to supply a treatment liquid stored in the tank; a check valve including a first inlet port connected to an outside air, and a first outlet port; a bubble tank into which the treatment liquid flows, the bubble tank including a floating matter discharge port arranged near a liquid surface of the treatment liquid, the floating matter discharge port configured to discharge a floating matter floated on the treatment liquid, and wherein the bubble tank includes a second inlet port arranged in a lower portion of the bubble tank; a microbubble generator arranged outside the bubble tank, the microbubble generator configured to generate microbubbles by mixing air into the treatment liquid supplied from the liquid supply pump, and wherein the microbubble generator includes a treatment liquid inlet connected to the liquid supply pump, an air inlet connected to the first outlet port, and a second outlet port connected to the second inlet port; a separation tank connected to the bubble tank at a lower portion of the bubble tank; and a circulation pipe configured to return the treatment liquid overflown from the liquid surface in the separation tank to the tank, wherein an opening at the upper end of the circulation pipe serves as a circulation port, wherein the height of the liquid surface of the treatment liquid is determined by a position of the circulation port; wherein the floating matter discharge port is disposed at substantially the same height as the circulation port or slightly higher than the circulation port; wherein the bubble tank includes a bubble outlet arranged at upper portion of the bubble tank, wherein the bubble outlet is located above the circulation port, the lower end of the bubble outlet being located surely above the liquid surface, the liquid treatment apparatus further comprising: a collecting trough arranged below the bubble outlet, the collecting trough configured to collect the floating matter discharged from the bubble outlet; and a defoaming pump including a suction port connected to the collecting trough, and a discharge port connected to the bubble tank. a tank; a liquid supply pump configured to supply a treatment liquid stored in the tank; a check valve including a first inlet port connected to an outside air, and a first outlet port; a first inlet port connected to an outside air, and a first outlet port; a bubble tank into which the treatment liquid flows, the bubble tank including a floating matter discharge port arranged near a liquid surface of the treatment liquid, the floating matter discharge port configured to discharge a floating matter floated on the treatment liquid, and wherein the bubble tank includes a second inlet port arranged in a lower portion of the bubble tank; a microbubble generator arranged outside the bubble tank, the microbubble generator configured to generate microbubbles by mixing air into the treatment liquid supplied from the liquid supply pump, and wherein the microbubble generator includes a treatment liquid inlet connected to the liquid supply pump, an air inlet connected to the first outlet port, and a second outlet port connected to the second inlet port; a treatment liquid inlet connected to the liquid supply pump, an air inlet connected to the first outlet port, and a second outlet port connected to the second inlet port; a separation tank connected to the bubble tank at a lower portion of the bubble tank; and a circulation pipe configured to return the treatment liquid overflown from the liquid surface in the separation tank to the tank, wherein an opening at the upper end of the circulation pipe serves as a circulation port, wherein the height of the liquid surface of the treatment liquid is determined by a position of the circulation port; wherein the floating matter discharge port is disposed at substantially the same height as the circulation port or slightly higher than the circulation port; wherein the bubble tank includes a bubble outlet arranged at upper portion of the bubble tank, wherein the bubble outlet is located above the circulation port, the lower end of the bubble outlet being located surely above the liquid surface, the liquid treatment apparatus further comprising: a collecting trough arranged below the bubble outlet, the collecting trough configured to collect the floating matter discharged from the bubble outlet; and a defoaming pump including a suction port connected to the collecting trough, and a discharge port connected to the bubble tank. a collecting trough arranged below the bubble outlet, the collecting trough configured to collect the floating matter discharged from the bubble outlet; and a defoaming pump including a suction port connected to the collecting trough, and a discharge port connected to the bubble tank. a suction port connected to the collecting trough, and a discharge port connected to the bubble tank.