Cell counting is a method used to quantify cells for disease diagnosis and medical research. Generally, hemocytometer is used to count cells as it is a cheaper and simple method. Specimen contains cells is loaded into the hemocytometer and placed on a microscope. The coarse adjusting knobs of microscope are turned to focus the cells. For a beginner user, to get focused cells is time-consuming. If the user too harsh with the adjusting knob, it may loosen the knob gear. Moreover, if the cells are too over focused, it may cause damage to the objective lens and the hemocytometer. In order to overcome these problems, an autofocus system is developed to control the movement of adjusting knob in achieving the focused image automatically. A CCD camera is attached to the microscope to capture images of cells via gigabit Ethernet. The images are then analyzed using contrast measurement method. To control the movement of knob, an attachable stepper motor is used. The movement is stopped when the focused image is achieved. As a result, the autofocus system could assist a user to focus cells faster and make the microscope become more user-friendly.