An apparatus for inspecting a collimator including a pigtail formed with first and second fibers, a GRIN lens disposed coaxially relative to the pigtail, and a glass tube supporting the pigtail and the GRIN lens in a single unit, to inspect optical properties of the collimator, comprising an inspection table; a gripping part, which is provided on the inspection table, gripping the collimator subject to inspection; a light supplying part transmitting a predetermined optical signal to the first fiber; a light receiving part, which is connected to the second fiber, receiving an optical signal returned from the second fiber, entering the first fiber; a measuring part calculating a value of the predetermined optical signal, which entered the first fiber, and a value of the optical signal, which returned from the second fiber; and an image displaying part displaying the value obtained from the measuring part. With this configuration, the collimator can be inspected in part, thereby increasing the product reliability of the collimator.