An electrochemical automatic analyzer comprising: a detection unit (131, 232, 301∼309) including a working electrode in which platinum, gold, or carbon occupies 50% or more of an elemental composition of a surface thereof, counter electrodes (304, 305), a saturated silver-silver chloride electrode potential reference and an ammeter; a means for introducing a measurement liquid containing a component to be measured bound to magnetic particles and a measurement solvent into the detection unit; a voltage applying means for applying a voltage of +1.2 V or more with respect to the saturated silver-silver chloride electrode potential reference to the working electrode; a magnetic field applying means for applying a magnetic field such that the component to be measured bound to the magnetic particles is supplemented on the working electrode; a degassing means (246, 703) for degassing a gas from the measurement solvent before the measurement solvent is introduced into the detection unit, wherein the degassing means is an inert gas supply mechanism including an electrochemically inert gas and adapted to perform purging of the measurement solvent by the inert gas or the degassing means is a degasifier including a gas-liquid separation film to remove a dissolved gas from the measurement solvent; a dissolved oxygen analyzer in the detection unit, to measure a degassed state of the measurement solvent; and a control unit configured to control the automatic analyzer so as to introduce the measurement solvent degassed by the degassing means (246, 703) onto the working electrode in the detection unit to discharge a coexisting component that is not bound to magnetic particles out of the system, to apply the voltage to the working electrode using the voltage applying means while the detection unit is filled with the measurement solvent, and to measure a current response generated between the working electrode and the counter electrodes (304, 305) using the ammeter, said response depending on the concentration of the component to be measured. a detection unit (131, 232, 301∼309) including a working electrode in which platinum, gold, or carbon occupies 50% or more of an elemental composition of a surface thereof, counter electrodes (304, 305), a saturated silver-silver chloride electrode potential reference and an ammeter; a means for introducing a measurement liquid containing a component to be measured bound to magnetic particles and a measurement solvent into the detection unit; a voltage applying means for applying a voltage of +1.2 V or more with respect to the saturated silver-silver chloride electrode potential reference to the working electrode; a magnetic field applying means for applying a magnetic field such that the component to be measured bound to the magnetic particles is supplemented on the working electrode; a degassing means (246, 703) for degassing a gas from the measurement solvent before the measurement solvent is introduced into the detection unit, wherein the degassing means is an inert gas supply mechanism including an electrochemically inert gas and adapted to perform purging of the measurement solvent by the inert gas or the degassing means is a degasifier including a gas-liquid separation film to remove a dissolved gas from the measurement solvent; a dissolved oxygen analyzer in the detection unit, to measure a degassed state of the measurement solvent; and a control unit configured to control the automatic analyzer so as to introduce the measurement solvent degassed by the degassing means (246, 703) onto the working electrode in the detection unit to discharge a coexisting component that is not bound to magnetic particles out of the system, to apply the voltage to the working electrode using the voltage applying means while the detection unit is filled with the measurement solvent, and to measure a current response generated between the working electrode and the counter electrodes (304, 305) using the ammeter, said response depending on the concentration of the component to be measured.