To provide a displacement detection sensor for brake pedal having a stop lamp switch function, capable of efficiently securing an installation space while reducing the cost and weight.

The sensor includes: a permanent magnet 7 which is integrally joined to the center on one side of a magnet case 5 facing a sensor housing 1; a sensor lever 11 which rotates the magnet case when a brake pedal 9 is rotated; an electronic circuit board 13; and a Hall element which generates a current corresponding to the magnetic field generated from the permanent magnet when the permanent magnet is rotated. A controller converts the current to an electric signal corresponding to a rotation displacement of the brake pedal and outputs it. The controller further outputs a control signal for lighting a stop lamp provided on a vehicle when the value of the converted electric signal is a preset set value or more, and outputs a control signal for extinguishing the stop lamp when the value of the converted electric signal is below the set value.