A light source position detection apparatus , comprising: a condensing section that condenses light emitted from a light source to be detected; an image pickup device that receives the light condensed by the condensing section ; infrared light image forming means for forming an image of infrared light that passes through clouds on the image pickup device , out of light emitted from the light source to be detected without forming any image of visible light on the image pickup device ; and a control section , wherein the control section performs: a first acquisition process of acquiring per-pixel brightness information from the image pickup device ; a process of changing a shutter speed based on the brightness information acquired in the first acquisition process and adjusting the quantity of light received by the image pickup device ; a second acquisition process of acquiring per-pixel brightness information from the image pickup device , the shutter speed of which is changed; a process of setting brightness information equal to or less than a threshold set to a value greater than brightness caused by light scattered by clouds out of the brightness information acquired in the second acquisition process to zero; and a process of detecting the position of the light source to be detected based on brightness information after the setting to zero process. a condensing section that condenses light emitted from a light source to be detected; an image pickup device that receives the light condensed by the condensing section ; infrared light image forming means for forming an image of infrared light that passes through clouds on the image pickup device , out of light emitted from the light source to be detected without forming any image of visible light on the image pickup device ; and a control section , wherein the control section performs: a first acquisition process of acquiring per-pixel brightness information from the image pickup device ; a process of changing a shutter speed based on the brightness information acquired in the first acquisition process and adjusting the quantity of light received by the image pickup device ; a second acquisition process of acquiring per-pixel brightness information from the image pickup device , the shutter speed of which is changed; a process of setting brightness information equal to or less than a threshold set to a value greater than brightness caused by light scattered by clouds out of the brightness information acquired in the second acquisition process to zero; and a process of detecting the position of the light source to be detected based on brightness information after the setting to zero process. a first acquisition process of acquiring per-pixel brightness information from the image pickup device ; a process of changing a shutter speed based on the brightness information acquired in the first acquisition process and adjusting the quantity of light received by the image pickup device ; a second acquisition process of acquiring per-pixel brightness information from the image pickup device , the shutter speed of which is changed; a process of setting brightness information equal to or less than a threshold set to a value greater than brightness caused by light scattered by clouds out of the brightness information acquired in the second acquisition process to zero; and a process of detecting the position of the light source to be detected based on brightness information after the setting to zero process. <EOS>