A water quality improving unit (1) and a water quality improving device which enhance water transparency by removing organic matters allowed to float on the water surface with micro-bubbles (X2) attached, and can improve water quality by balancing dissolved gases such as oxygen gas and nitrogen gas. The water quality improving unit comprises a unit body (2) having a hollow portion formed almost rotationally-symmetric and reduced in diameter toward the both axial directions of the rotationally symmetric axis, a liquid introducing hole opened in the peripheral wall of the unit body (2) in a tangential direction, vertically-directed gas-liquid jet holes (3) disposed to be opened in a vertical direction along the axial direction of the rotationally symmetric axis of the hollow portion, and respectively provided in the both diameter-reduced portions of the hollow portion, a frame-carrying pipe (4) connected with the upward-directed gas-liquid jet hole (3) with some gap between them, and a liquid bubble generating container (6) connected with the upside unit body (2) portion in order to form liquid jetted from the upward-directed gas-liquid jet hole (3) into a cluster (a bubble cluster in a soap bubble form) of liquid bubbles (X3).
