Abstract: A light-emission measuring apparatus which is capable of eliminating various secondary problems in addition to shutting off strong light from the external and preventing crosstalk. The light-emission measuring apparatus is equipped with a box-type carrier 9 having an open top surface and made to accommodate a microplate 7 comprising a plurality of wells. The box-type carrier is disposed to be movable horizontally. A light-obstruction plate having a light-receiving hole 11 is disposed above the box-type carrier to be movable vertically. The light-obstruction plate 5 is brought into tight contact with a circumference of the box-type carrier 9 to establish a black box when being moved downwardly. Further, the light-receiving hole 11 of the light-obstruction plate 5 has a cylindrical projecting bottom surface 12 so that its bottom surface side outer circumference comes into tight contact with a circumference 13 of an opening of a well top surface of the microplate 7.