A device that divides light into eight, four or two beams of equivalent power with only minor total power loss was designed, built and tested. The apparatus accepts light from a 200 μm diameter, 0.16 numerical aperture, silica–silica multimode optical fiber connected to one of several laser light sources for photodynamic therapy (PDT) of cancer. The incorporation of a variable iris diaphragm into the optical couplers allows the power of the beams to be independently set. Each of the beams can be coupled to a 400 or 600 μm diameter optical fiber to deliver the therapeutic light to the patient. This device is used in our institute for PDT of patients with either numerous small malignant tumors or single tumors with large surface area.