A light source unit which is reduced in size while securing a certain quantity of light by increasing the utilization efficiency of light and a projector system utilizing the light source unit. The light source unit includes a reflector whose internal surface is planished to provide a mirror reflection effect and which is formed with a lamp accommodation opening and a light emitting opening, a light source including a bulb which radiates light and a lamp comprising an electrode introducing portion that guides electrodes into the bulb, and a condenser which lies on an optical axis of the light radiated from the lamp and which is adapted to gather the light that is radiated from the lamp and that is reflected on the reflector.