Provided are a magnetic marker and magnetic marker detection system in which magnetic force is suppressed. This magnetic marker detection system 1S, which detects, by means of a magnetic sensor 2 that is attached to a vehicle body floor 50 of a vehicle 5, magnetism generated by a magnetic marker 1 laid on a road surface 53, combines a magnetic marker 1, of which the magnetism attainment ratio Gh/Gs which is the ratio of the magnetic flux density Gh at a position at a height of 250mm to the magnetic flux density Gs at the surface is 0.5% or more, and a magnetic sensor, which uses a magnetoimpedance element that includes a magnetosensitive body of which the impedance changes in accordance with an external magnetic field.