To provide a magnetic liquid level detection device having reduced detection errors caused by the fluctuation of the facing distance between a magnet whose position is displaced sequentially with a float floating on the liquid surface and a magnetic resistance element facing to the magnet.

The magnetic resistance element 14a mounted on a substrate 14 in a housing member 15 of this magnetic liquid level detection device 10 is faced to the magnet 13 and arranged close to the rotation center of an arm 12, and a discoid magnet holding part 18 for holding the magnet 13 on an arm 12 support member for supporting the arm 12, into which the base end 12b of the arm is inserted. The peripheral part 18b (or a protrusion part provided along the peripheral part 18b) of the magnet holding part 18 is allowed to abut slidably on the housing member 15, to thereby regulate the inclination of the arm 12 in the separating direction from the substrate 14 around the base end 12b.