An extreme ultraviolet (EUV) light source device and foil trap, the device including a vessel; an EUV radiating species supply means that feeds an extreme ultraviolet radiating species into the vessel; a discharge part with discharge electrodes that heat and excite the EUV radiating species and generate a high-temperature plasma; a collector mirror collecting EUV radiation emitted from the plasma; the foil trap installed between the discharge part and the mirror; an extractor part extracting the collected radiation; and an evacuation means exhausting and regulating pressure within the vessel. The foil trap includes foils extending radially from a main axis thereof to capture debris from the light source, while allowing the emitted radiation to pass through a region thereof to the mirror. A length of at least part of the foils in directions parallel to the main axis is shorter in positions close to the main axis than distant therefrom.