Provided are a biomagnetism measuring device, a biomagnetism measuring system, and a biomagnetism measuring method, which measure biomagnetism with high precision using magnetic sensors that can be used at room temperature. According to the embodiment, biomagnetism is measured based on output signals which correspond to changes in the resistance of tunneling magnetoresistance elements (TMR elements 67). A magnetic sensor which outputs a single unit output signal is configured of a TMR array (68), which comprises TMR elements arrayed in a lattice between input and output electrodes. Each magnetic sensor is positioned in either a single-axis direction or in mutually intersecting two-axis or three-axis directions, and is brought close to a portion of the surface of a subject (i.e., the head). A plurality of said magnetic sensors are distributed upon said portion of the surface of the subject, whereupon the output signals are obtained from the plurality of magnetic sensors, and the biomagnetism emitted from the portion of the surface of the subject is measured based on the output signals.
