An oil-cooled screw compressor comprising: a housing in which a screw chamber, seal chambers positioned on both sides of the screw chamber, bearing chambers in communication with the screw chamber via the seal chambers, a tooth surface lubricating fluid flow path through which the tooth surface lubricating fluid is supplied to the screw chamber, and a bearing lubricating fluid flow path through which the bearing lubricating fluid is supplied to the bearing chambers, are defined; male and female screw rotors (24, 26) each including: a screw (24a, 26a) that is disposed in the screw chamber and forms a compression chamber; and shafts (24b, 26b) that coaxially extend from both ends of the screw (24a, 26a) to be disposed in the seal chambers and the bearing chambers; a plurality of bearings that are disposed in the bearing chambers, and rotatably support the respective shafts; and seal devices that are disposed in the respective seal chambers, and each seal a circumference of a corresponding one of the shafts, the seal devices each include: a first seal unit that is disposed on a side of the screw chamber in the corresponding seal chamber; and a second seal unit that is disposed on a side of the bearing unit in the seal chamber, the second seal unit and the first seal unit defining a separation gas supply gap therebetween, the seal chambers include: a discharge side seal chamber that is positioned on a discharge side of the compression chamber; and an intake side seal chamber that is positioned on an inlet side of the compression chamber, characterized in that in the housing, a separation gas supply path through which the separation gas is supplied into the separation gas supply gap, and a pressure balancing path through which an area closer to the screw chamber than the first seal unit in the discharge side seal chamber is in communication with the compression chamber under a pressure higher than an inlet pressure of the target gas sucked into the oil-cooled screw compressor and lower than a discharge pressure of the target gas discharged from the oil-cooled screw compressor, are defined in addition to the tooth surface lubricating fluid flow path and the bearing lubricating fluid flow path, and a check valve that restricts a flow of a fluid in a direction from the screw chamber to the discharge side seal chamber is disposed in the pressure balancing path. a housing in which a screw chamber, seal chambers positioned on both sides of the screw chamber, bearing chambers in communication with the screw chamber via the seal chambers, a tooth surface lubricating fluid flow path through which the tooth surface lubricating fluid is supplied to the screw chamber, and a bearing lubricating fluid flow path through which the bearing lubricating fluid is supplied to the bearing chambers, are defined; male and female screw rotors (24, 26) each including: a screw (24a, 26a) that is disposed in the screw chamber and forms a compression chamber; and shafts (24b, 26b) that coaxially extend from both ends of the screw (24a, 26a) to be disposed in the seal chambers and the bearing chambers; a plurality of bearings that are disposed in the bearing chambers, and rotatably support the respective shafts; and seal devices that are disposed in the respective seal chambers, and each seal a circumference of a corresponding one of the shafts, the seal devices each include: a first seal unit that is disposed on a side of the screw chamber in the corresponding seal chamber; and a second seal unit that is disposed on a side of the bearing unit in the seal chamber, the second seal unit and the first seal unit defining a separation gas supply gap therebetween, a first seal unit that is disposed on a side of the screw chamber in the corresponding seal chamber; and a second seal unit that is disposed on a side of the bearing unit in the seal chamber, the second seal unit and the first seal unit defining a separation gas supply gap therebetween, the seal chambers include: a discharge side seal chamber that is positioned on a discharge side of the compression chamber; and an intake side seal chamber that is positioned on an inlet side of the compression chamber, a discharge side seal chamber that is positioned on a discharge side of the compression chamber; and an intake side seal chamber that is positioned on an inlet side of the compression chamber,