A magnetic field detection device, containing a) a first soft magnetic body containing a1) a first plate including a first surface having a first outer edge; and a2) a first protrusion disposed directly or indirectly on the first surface of the first plate at a first arrangement position set back from the first outer edge, the first protrusion including a first tip on an opposite side to the first surface; and b) a magnetic detector provided in a vicinity of the first tip, wherein the magnetic detector has a magnetic sensing direction along the first surface, and the first protrusion is capable of bending a direction of a first magnetic flux, which comes into the first plate, along the first surface.