A microplate reader includes a light emitting portion for irradiating each of a plurality of test samples with excitation light, a light receiving portion for receiving return light from each of the test samples, and an XY stage for moving the light emitting portion and the light receiving portion to traverse and scan the test samples. The light emitting portion and the light receiving portion are defined at the same location on a reflection surface, which is formed on a distal end of a glass light guide rod. The light emitting portion irradiates each test sample with a sufficient amount of excitation light so that a sufficient amount of return light enters the light receiving portion.