Sample detector and measurement device equipped with the same

A sample detector B includes a member provided with an aperture , as well as a light receiving element which receives two light beams directed from a pair of light sources to a detection area AR and having passed through the detection area and outputs a signal corresponding to the amount of light received, and a determination means for determining whether or not a sample is properly supplied to the detection area AR based on the signal. Two light beams emitted from the paired light sources travel through paths defined by the aperture to regions ARr, ARf of the detection area AR which are positionally deviated from each other. With this arrangement, whether or not a sample is properly supplied to the detection area AR is precisely determined without using an expensive component such as an optical lens.