A collet chuck is provided to easily detach/attach an instrument without an additional instrument by using a spring and a bush which are connected to an instrument connection unit. A connection unit of a rectangular shape is formed on a side to process an object. An instrument having a processing unit is fixed on the other side. An installation holder(10) is connected to a chuck which is formed on the object. A sank unit which is connected to the chuck of the object is formed on a side of the installation holder. A screw unit is formed on the other side of the installation holder. A hollow unit is formed on the inside of the installation holder. An instrument connection unit is inserted into the hollow unit of the installation holder. A spring is connected to an inner side of the instrument connection unit. A collet(50) is connected to a side of the spring. The collet has a bush which is movably formed on an inner/outer side by the spring to clamp the instrument. A nut(60) has a female screw unit which is connected to a male screw unit of the installation holder. The nut has a connection groove of a cam shape connected to the instrument connection unit.
