To provide a spectrophotometer capable of automatically adjusting a maximum signal amount around an upper limit of an input range of an A/D converter, and maintaining stability and accuracy of a measured value at a best level when a specimen measurement part is replaced.

A specific IC tag 16 is attached on the specimen measurement part 3, and an identification signal for identifying a type of the specimen measurement part 3 from the IC tag is sent to a receiver 17 attached on a photometric-control part 7. The photometric-control part 7 recognizes the type of the specimen measurement part 3 from the identification signal, and turns on and off a switch 10 for selecting a resistance value of an amplification circuit 5 to change an amplification factor of the amplification circuit 5. Thereby, input to the A/D converter 6 is maintained constantly at a same level.