A light source device for endoscopes includes a light source; a condenser lens unit for collecting light beams from the light source; a light guide for receiving the light beams collected through the condenser lens unit into its entrance end face to transmit them to its exit end face; and a reflecting mirror located on the opposite side of the condenser lens unit with respect to the light source. The light source device is designed so that a position where the light beams emitted from the light source are collected directly through the condenser lens unit does not coincide with a position where the light beams emitted from the light source and reflected back to the light source by the reflecting mirror are collected through the condenser lens unit. In an embodiment, an arc axis of the light source is substantially parallel to the optical axis of the condenser lens unit. In another embodiment, direct light and reflected light each enter an entrance face of a forked light guide. In another embodiment, an infra-red removing filter is interposed between a front lens and a rear lens of the condenser unit.