To provide a work chuck device for gripping a work without deforming the same and reducing a chuck open and close time.

This device is provided with: a chuck including a plurality of chuck members 8 and gripping the work W; a cylinder device 7 opening and closing the chuck members 8; and a pressurized fluid supply circuit 13. The pressurized fluid supply circuit 13 is provided with a high low pressure switching means 18 switching pressure of fluid supplied to the cylinder device 7 to high pressure or low pressure. A circuit control means 25 controlling the pressurized fluid supply circuit 13 is provided with a high low pressure switching control means 26. The high low pressure switching control means 26 controls the high/low pressure switching means 18 to maintain a transmitting route part Sa in a side from a middle position of a transmitting route which is opened and closed by the chuck 5 to grip the work W at low pressure and a transmitting route part Sb in a side far from the work W at high pressure.