An access control device controls access to a first device and a second device. The first device is connected with a first bus conforming to a first standard and conforms to the first standard. The second device is connected with the first bus and conforms to a second standard. The access control device includes a first signal generator and a second signal generator. The first signal generator generates a first transaction start signal indicating start of a transaction for the first device. The second signal generator generates a second transaction start signal for the second device based on the first transaction start signal.