A computer mouse includes a left key assembly, a right key assembly, a signal processing unit, and a casing. The casing includes a top casing and a bottom casing. The bottom casing includes a bottom convex surface, the contour of the bottom convex surface is an ellipse, the bottom casing defines two first openings in the bottom convex surface, and the two key assemblies are positioned in the corresponding first openings. Each of the left key assembly and the right key assembly includes a hollow receiving column, a movable shaft, an elastic member and a pressure sensor. The movable shaft is received in the receiving columns. The movable shaft and the pressure sensor are spaced from each other via the elastic element. The pressure sensor will generate a corresponding pulse when pressed by the movable shaft. The signal processing unit receives the pulse, and sends a controlling signal.