A quantum-yield measurement device for measuring a quantum yield of a sample by irradiating a sample container of a sample cell for containing the sample with pumping light and detecting light to be measured emitted from at least one of the sample and sample container, the device comprising: a dark box for arranging therein the sample container, the dark box having a first opening and a first shutter, a second opening and a second shutter, a third opening and a third shutter, and a fourth opening and a fourth shutter; a light generation unit, having a light exit part connected to the dark box, for generating the pumping light; a light detection unit, having a light entrance part connected to the dark box, for detecting the light to be measured; an integrating sphere, arranged within the dark box, having a light entrance opening for the pumping light to enter and a light exit opening for the light to be measured to exit; a movement mechanism for moving the sample container, the light exit part, and the light entrance part such that the sample container attains each of a first state of being located inside of the integrating sphere and a second state of being located outside of the integrating sphere, and causing the light exit part to oppose the light entrance opening and the first opening, and causing the light entrance part to oppose the light exit opening and the third opening, for detecting light to be measured in the first state; the movement mechanism further causing the light exit part to oppose the second opening and the light entrance part to oppose the fourth opening, for detecting light to be measured in the second state, and wherein the first and third shutters (63 and 66) are opened and the second and fourth shutters (70 and 68) are closed in the first state, and further wherein the second and fourth shutters (70 and 68) are opened and the first and third shutters (63 and 66) are closed in the second state. a dark box for arranging therein the sample container, the dark box having a first opening and a first shutter, a second opening and a second shutter, a third opening and a third shutter, and a fourth opening and a fourth shutter; a light generation unit, having a light exit part connected to the dark box, for generating the pumping light; a light detection unit, having a light entrance part connected to the dark box, for detecting the light to be measured; an integrating sphere, arranged within the dark box, having a light entrance opening for the pumping light to enter and a light exit opening for the light to be measured to exit; a movement mechanism for moving the sample container, the light exit part, and the light entrance part such that the sample container attains each of a first state of being located inside of the integrating sphere and a second state of being located outside of the integrating sphere, and causing the light exit part to oppose the light entrance opening and the first opening, and causing the light entrance part to oppose the light exit opening and the third opening, for detecting light to be measured in the first state; the movement mechanism further causing the light exit part to oppose the second opening and the light entrance part to oppose the fourth opening, for detecting light to be measured in the second state, and wherein the first and third shutters (63 and 66) are opened and the second and fourth shutters (70 and 68) are closed in the first state, and further wherein the second and fourth shutters (70 and 68) are opened and the first and third shutters (63 and 66) are closed in the second state.