A semiconductor memory device having an externally controllable input and output mode is provided. The semiconductor memory device includes a first and second plurality of pads and an input and output mode set circuit electrically connected to the first plurality of pads and the second plurality of pads, for generating a plurality of input and output mode signals. The input and output mode set circuit cuts off signals received from the first plurality of pads, controls the level of each of the input and output mode signals to be at either a logic high level and a logic low level, and sets the input and output mode when a voltage higher than the supply voltage of the semiconductor memory device is applied to one of the second plurality of pads in a test mode. The high voltage is not applied to the second plurality of pads and the input and output mode set circuit controls the level of the input and output mode signals to be at either a logic high level or a logic low level, and thus sets the semiconductor memory device to have one input and output mode responsive to signals received from the plurality of pads, during a normal operation. Accordingly, it is possible to externally change the input and output mode of the semiconductor memory device.