A signal testing apparatus includes a number of first switches, a second switch, and a testing terminal. Each first switch includes a static contact, a first dynamic contact, and a second dynamic contact. The second switch includes a static contact and a number of dynamic contacts. When the static contact and the first dynamic contact of each first switch are connected to each other, a computer interface is connected to a peripheral equipment interface. When the static contact and the second dynamic contact of each first switch are connected to each other, the computer interface is disconnected to the peripheral equipment interface, the static contact of the second switch is capable of selectively connected to one of the dynamic contacts of the second switch, to selectively test a signal output from a corresponding pin of the computer interface.