A magnetic sensor system includes a scale and a magnetic sensor arranged in a relative positional relationship variable in a first direction, and a computing unit. The magnetic sensor includes a first detection circuit disposed at a first position and a second detection circuit disposed at a second position. Each of the first and second detection circuits includes a spin-valve magnetoresistive element. The difference between the first position and the second position in the first direction is smaller than or equal to 1.25% of a one-pitch amount of change in the relative positional relationship between the scale and the magnetic sensor. The computing unit generates an abnormal-event determination signal indicative of the presence of an abnormal event in the magnetic sensor by computation using detection signals from the first and second detection circuits.