A convey mechanism is a moving mechanism used to move a rack, which can store cuvettes, along a linear moving direction. A driving unit drives the convey mechanism to intermittently move the rack along. A detection unit outputs an error signal when it detects that a placement state of the rack on the convey mechanism corresponds to an error placement which does not allow the convey mechanism to normally convey the rack, and does not output any error signal when it detects that the placement state does not correspond to the error placement. A controller controls the driving unit to stop a convey operation of the rack when the error signal is output. The controller controls the driving unit to execute the convey operation of the rack when the error signal is not output.