Patent ID: 8324561

Claim:
A photodetecting device comprising: an integrating element having a spherical inner wall and configured to observe light to be measured generated according to irradiation of a sample with excitation light; and a sample holder to be removably attached to the integrating element, wherein the integrating element has an excitation light introducing hole for introducing excitation light and a sample introducing hole for introducing a cell held by the sample holder, the cell has a prismatic part, and a branch tube connected to the prismatic part, and the sample holder is locked to the sample introducing hole, and has a holding part which holds the branch tube of the cell for accommodating the sample and positioning means for disposing the cell with the branch tube has an axis so that an entrance surface of the cell, through which the excitation light enters the cell, and an exit surface of the cell parallel to the entrance surface incline relative to a surface perpendicular to the optical axis of the excitation light.