An attachment unit for attachment of a reaction container including a channel filled with a reaction solution containing a fluorescent probe and a liquid having a specific gravity different from that of the reaction solution and being immiscible with the reaction solution, the reaction solution moving close to opposed inner walls, a first heating unit heating a first region of the channel and a second heating unit heating a second region of the channel when the reaction container is attached to the attachment unit, a drive mechanism switching arrangement of the attachment unit, the first heating unit, and the second heating unit between a first arrangement and a second arrangement in which a lowermost position of the channel is located within a first region and a second region, respectively, a measurement unit measuring light intensity, and a control unit controlling the portions described above.