The dual‐variable detection method is a device to provide a wider dynamic range to the light intensity measurement by a photomultiplier. A dynamic range as wide as seven orders of magnitude is attainable by controlling and analyzing both the dynode voltage and the anode current. The electronic circuit is illustrated and its application to the simultaneous measurement of the absorbance and the circular dichroism, which have used to require different light intensity range for the optimum operation, is described.