An antifuse physically unclonable function (PUF) unit includes a first sub-antifuse cell, a second sub-antifuse cell, a connection circuit, a first copying circuit and a first reading circuit. The first sub-antifuse cell includes a first antifuse transistor. The second sub-antifuse cell includes a second antifuse transistor. The connection circuit is connected between a source/drain terminal of the first antifuse transistor and a source/drain terminal of the second antifuse transistor. The first copying circuit is connected with the first sub-antifuse cell, and includes a third antifuse transistor. The first reading circuit is connected with the first copying circuit. Moreover, the first reading circuit generates a random code according to a state of the third antifuse transistor.