A key assembly comprises a base plate and a key. The base plate has an opening defined therein. The key is accommodated in the opening, and includes a first key section, a second key section connecting with the first key section and a shaft portion protruding from the junction of the first key section and the second key section. The shaft portion is rotatably mounted to the housing. The key further includes two contacting members, one contacting member is mounted on the first key section, another contacting member is mounted on the second key section. When the first key section is pressed to rotate about the shaft portion, the contacting member mounted on the first key section moves in a direction of pressing the first key section and the contacting member mounted on the second key section moves in a direction reverse to the direction that the contacting member mounted on the first key section moves.