An apparatus for detecting the position of a collimator in a sputter-processing chamber is disclosed in the present invention. A target holder is at the upper portion of the chamber and a target is attached to the bottom surface of the target holder. A substrate holder is at the underlying portion of the chamber and it is opposed to the target holder. A silicon wafer is putted on the substrate holder. Two supporters are on an inner surface of the housing of the chamber and are separated to oppose to each other, the supporters protrude the housing. A collimator is putted on the supporters and it is parallel to the surface of the target. Two sensors is attached on the under surface or the lateral surface of the supporters. The horizontal height of the sensors is lower than that of the collimator. When the collimator is heated and it distorts, the position of the collimator will change to enter into the available area of the sensors. Afterwards, an alarm will announce a notice to supervisors of the sputtering system.