A blood (K) detector (10) capable of viewing the position of a blood vessel (K) by viewing a reflected light from a muscle (I) after being transmitted into the muscle (I) by the radiation of the light onto the surface of a skin (S), comprising a light shielding tube (20) having a skin contact part allowing to abut on the skin (S) formed at the tip side thereof and an eye contact part formed on the base side thereof and light emitting members (30) disposed around the light shielding tube (20) and radiating light beam toward the skin (S).
