A marker detection method of detecting magnetic markers laid in a road and arranged at spacings along a lane by using a vehicle side magnetic detection unit with a plurality of magnetic sensors (Cn) arranged in a vehicle width direction, the method comprising: a marker detection process for detecting the magnetic markers, in which it is determined that the magnetic detection unit is positioned straight above a respective one of the magnetic markers using first magnetic distribution data that is a distribution of magnetic measurement values in the forwarding direction, and a lateral shift amount of the vehicle in the vehicle width direction with reference to the respective one of the magnetic markers is identified using second magnetic distribution data that is a distribution of magnetic measurement values in the vehicle width direction; and a determination process, including detecting a center position of a magnetic distribution in the vehicle width direction acting on the magnetic detection unit in each cycle of acquisition of the second magnetic distribution data which is executed with a certain time frequency, and determining a possibility of a presence of a magnetic generation source that causes disturbance by processing an index representing a degree of a positional change of the center position when the vehicle travels the road. a marker detection process for detecting the magnetic markers, in which it is determined that the magnetic detection unit is positioned straight above a respective one of the magnetic markers using first magnetic distribution data that is a distribution of magnetic measurement values in the forwarding direction, and a lateral shift amount of the vehicle in the vehicle width direction with reference to the respective one of the magnetic markers is identified using second magnetic distribution data that is a distribution of magnetic measurement values in the vehicle width direction; and it is determined that the magnetic detection unit is positioned straight above a respective one of the magnetic markers using first magnetic distribution data that is a distribution of magnetic measurement values in the forwarding direction, and a lateral shift amount of the vehicle in the vehicle width direction with reference to the respective one of the magnetic markers is identified using second magnetic distribution data that is a distribution of magnetic measurement values in the vehicle width direction; and a determination process, including detecting a center position of a magnetic distribution in the vehicle width direction acting on the magnetic detection unit in each cycle of acquisition of the second magnetic distribution data which is executed with a certain time frequency, and determining a possibility of a presence of a magnetic generation source that causes disturbance by processing an index representing a degree of a positional change of the center position when the vehicle travels the road. detecting a center position of a magnetic distribution in the vehicle width direction acting on the magnetic detection unit in each cycle of acquisition of the second magnetic distribution data which is executed with a certain time frequency, and determining a possibility of a presence of a magnetic generation source that causes disturbance by processing an index representing a degree of a positional change of the center position when the vehicle travels the road.