Disclosed herein is a spectrophotometer. The spectrophotometer includes a CPU having a signal prediction part and a comparison/calculation part. The signal prediction part predicts the strength of an output signal from a photodetection unit during the next period based on the strength of the output signal from the photodetection unit. The comparison/calculation part compares a reference value, which defines the limit value of electrical current passing through a photomultiplier tube, of the strength of an output signal from an AD converter with a predicted value predicted by the signal prediction part. In a case where the predicted value exceeds the reference value, a voltage applied to the photomultiplier tube is calculated so that the strength of an output signal from the photodetection unit during the next period does not exceed the reference value. An applied voltage control part is configured to perform applied voltage control based on an applied voltage value calculated by the comparison/calculation part when the predicted value of the strength of an output signal from the photodetection unit during the next period exceeds the reference value.