To determine the intensity of the violet indigo fluorescence produced from dehydro ascorbic acid and o-phenylenediamine, a fluorophotometer was devised. Practicability of this apparatus was confirmed by the parallelism between the concentration of the solution and intensity of photoelectric current, using riboflavin and thiochrome. The features of this apparatus are the avoidance of the use of mercury lamp, use of nitrofurazone compounds for the interception of the ultraviolet rays, use of individual voltage stabilizers for the light source and amplifiers to offset the variation of electric current at the source, and the increase in the intensity and providing for variability by the use of 10-step variable resistor.