1. A non-invasive blood component measuring device comprising: a light source section for illuminating a living body which includes a blood vessel; an imaging section for capturing a living body image of the living body illuminated by the light source section; a controller, including a memory under control of a processor, the memory storing instructions enabling the processor to carry out operations, comprising: calculating, based on an image of a blood vessel shown in the living body image, a concentration of a blood component in blood of the living body; determining a position of the image of the blood vessel in the living body image; generating a first luminance distribution representing a distributed luminance of pixels lined along the image of the blood vessel, the pixels being apart from the image of the blood vessel by a predetermined distance; obtaining, based on the first luminance distribution, an index which represents an amount of blood contained in a peripheral tissue of the blood vessel; and correcting, based on the index, the concentration of the blood component.