The present invention relates to an apparatus for testing a package-on-package semiconductor device, mainly comprising a pick-and-place device, a test socket, an upper chip holder, and a main controller. When a first package device is to be tested, the main controller controls the pick-and-place device to load the first package device into the test socket and then controls the pick-and-place device to transfer the upper chip holder and bring the upper chip holder into electrical contact with the first package device on the test socket so that a second package device in the upper chip holder is electrically connected to the first package device for testing. Accordingly, the upper chip holder is an independent component. Only when a test is executed, the pick-and-place device transfers the upper chip holder onto the test socket so that the second package device is electrically connected to the first package device.