A diamond magnetic sensor comprises: a diamond that has at least one NV-center; a microwave generator that irradiates the diamond with microwaves; an excitation light generator that irradiates the NV-center in the diamond with excitation light; and a fluorescence detector that receives fluorescent light generated by the NV-center in the diamond. The diamond magnetic sensor further comprises a pattern measurement device that measures time-change patterns in the magnetic field intensity from changes in the fluorescence intensity detected by the fluorescence detector.