An electromagnetic flow meter includes a measurement tube, an excitation coil, an excitation current supplying unit supplying an excitation current with an excitation frequency fex to the excitation coil, a pair of electrodes disposed inside the measurement tube, a measuring unit measuring a flow based on an emf that arises between the electrodes, a first A/D converting unit that converts the emf to a digital signal, a sampling unit sampling the digital signal, a noise evaluation value calculating unit, based on at least the sample data sampled by the sampling unit, calculating as a noise evaluation value the magnitude of the impact of a noise component owing to adherence of foreign matter to the electrodes upon the measurement of the flow, and an electrode scaling diagnosing unit determining an electrode foreign matter adherence state by comparing the noise evaluation value and a predetermined diagnostic threshold value.