A position detection system includes a first magnet, a first soft ferromagnetic member, and a magnetic detector. The first magnet is magnetized in a first direction and generates a first magnetic field including a first magnetic line. The first soft ferromagnetic member is rectilinearly movable along a second direction and includes a first outer edge having a first outer edge part remote from the first magnet by a first distance in a third direction and a second outer edge part remote from the first magnet by a second distance in the third direction. The first and second outer edge parts are disposed at different positions in the second direction. The magnetic detector is kept at a predetermined constant position relative to the first magnet. The first magnetic line passes through the magnetic detector in the first direction when the first soft ferromagnetic member is at rest.