To provide a workpiece adsorption device having a simple configuration capable of removing a grinding liquid containing sludge etc. in a maintenance-free fashion even if it sucks the liquid at the time of sucking and holding a lens by negative pressure.

A filter device 20 comprises a liquid storing case 22 having a space of a predetermined volume, suction piping 24 continuously extended and installed toward a lower side in the gravity direction from the liquid storing case 22 so as to connect the liquid storing case 22 and a lens holding part 14, evacuation piping 26 extended toward a vacuum generator 16 from an upper part in the gravity direction beyond the installation position of the suction piping 24 extended from the liquid storing case 22, and an obstacle structure 28 for preventing direct communication between the suction piping 24 and the evacuation piping 26 by the negative pressure in the liquid storing case 22. The filter device also comprises a valve 30 capable of setting the inside of the liquid storing case 22 to be in atmospheric pressure.