An adaptor structure includes a main adaptor, a first sub-adaptor, a second sub-adaptor and a first driving mechanism. The main adaptor is over a socket. The main adaptor has an opening. The first sub-adaptor is movably received in the opening of the main adaptor in a first direction. The first sub-adaptor is configured to support a first side surface of the semiconductor package. The second sub-adaptor is movably received in the opening of the main adaptor in the first direction and a second direction. The second sub-adaptor faces the first sub-adaptor to support a second side surface of the semiconductor package. The first driving mechanism is configured to move the second sub-adaptor in the second direction. Thus, the adaptor structure can guide the semiconductor packages having different sizes to the socket.