NOVELTY - The apparatus (2A) has a condensing unit (30) that concentrates ozone in ozone containing gas by separating waste acid matter from ozone containing gas generated by ozonizer (10). A discharge line (L23) discharges the acid matter and supply line (L24) passing along discharge line supplies the acid matter to primary side of ozonizer. A pressure regulation unit (90A) comprises booster pump (93) and back pressure valve (95) for adjusting supply pressure of waste acid gas supplied to the ozonizer. A microfluidic flow control unit (97) controls flow rate of the gas.    USE - Ozone gas concentration apparatus e.g. electronic component cleaning apparatus for cleaning semiconductor wafer, liquid crystal material, solar cell, organic electroluminescent display and printed circuit board.    ADVANTAGE - Since the supply pressure of the waste acid gas is adjusted, the pressure difference between waste acid gas and raw material oxygen gas supplied to the ozonizer can be avoided and the waste acid gas can be recycled efficiently. Hence, cost of the ozone concentration apparatus can be reduced and energy can be saved. The supply pressure adjustment can be performed easily and flow rate of the waste gas can be set appropriately. Since the residual ozone contained in the waste acid gas is decomposed, protection of the apparatus can be improved with simple structure and contamination of ozone containing gas can be prevented.    DETAILED DESCRIPTION - The apparatus includes a buffer chamber (96) in the primary side of the MFC unit and filter (94) in the secondary side of the booster pump. A thermal decomposition unit (92) decomposes residual ozone contained in the waste acid gas.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of the ozone concentration apparatus. (Drawing includes non-English language text)    Ozone concentration apparatus (2A)    Ozonizer (10)    Condensing unit (30)    Pressure regulation unit (90A)    Thermal decomposition unit (92)    Booster pump (93)    Filter (94)    Back pressure valve (95)    Buffer chamber (96)    Microfluidic flow control unit (97)    Discharge line (L23)    Supply line (L24)