In a metal halide lamp, xenon gas having a pressure of at least 3 atmospheres at room temperature and at least a metal halide including indium iodide are sealed in a discharge space not containing mercury. If the volume of the discharge space is denoted by V (mm.sup.3), the electric power applied to the arc tube by P (W), and the weight of the indium iodide by X (.mu.g), these parameters are set so as to satisfy a relationship (P/V)(X/V).sup.0.2>3.0. A continuous emission spectrum can thereby be produced by indium over the entire visible wavelength range, thus obtaining a mercury-free metal halide lamp that is usable as an excellent white light source suitable for data projectors, automobile lamps, headlights, and other systems and devices.