To provide a yield detecting magnetic resonance device capable of measuring easily a yield detecting magnetic resonance spectrum.

This yield detecting magnetic resonance device 10 is equipped with an electron spin resonance device 11 for reacting a sample 20a in a magnetic field and for irradiating a microwave to the sample 20a, and a flow- through type yield analyzer 18 connected to the electron spin resonance device 11 through a communicating passage 17. The flow-through type yield analyzer 18 analyzes the yield of a reaction product taken out from the electron spin resonance device 11 in the state where the reaction product is made to flow, and for example, a photodiode array detector used for liquid chromatograph or the like is used therefor. The flow-through type yield analyzer 18 analyzes the reaction product taken out from the electron spin resonance device 11 by making correspond to sweep of the magnetic field by a magnetic field sweeping mechanism 14 of the electron spin resonance device 11 to obtain the yield detecting magnetic resonance spectrum.