The present invention improves an S/N ratio and light intensity resolution provided by an A/D converter, and an analyzer includes: a measurement cell irradiated with light during sample measurement; a dimming element irradiated with the light during reference measurement; an amplifier configured to amplify an analog light intensity signal outputted from a light detector; an A/D converter configured to convert the analog light intensity signal into a digital light intensity signal; and an arithmetic device configured to calculate absorbance using a digital sample light intensity signal outputted from the A/D converter during the sample measurement and a digital reference light intensity signal outputted from the A/D converter during the reference measurement, wherein an amplification factor of the amplifier is set such that the analog reference light intensity signal and the analog sample light intensity signal become less than or equal to a full scale of the A/D converter.