Seat belt attachment/detachment detection switch

A seat belt attachment/detachment detection switch, comprising:

• a printed circuit board including a circuit for detecting attachment/detachment of a seat belt;
• a movable plate configured to slidably move along with insertion of a tongue plate of the seat belt;
• a rotor including a lever coupled to the movable plate, the rotor being rotatably attached to the printed circuit board to rotate as the tongue plate is pushed into a buckle;
• an electric brush attached to a surface of the rotor that faces the printed circuit board, the electric brush having leg parts that change a state of contact/non-contact with a conductive part of the circuit in accordance with a rotating state of the rotor;
• a protrusion provided at a tip of the lever, the protrusion protruding in a direction away from the printed circuit board and being inserted into a groove provided on the movable plate, wherein
• the groove includes
• a first linear part extending in a tongue plate extracting direction, and
• an inclination part positioned more in a tongue plate extracting direction than the first linear part and extending in the tongue plate extracting direction with an inclination at an angle θ, provided that θ<90°, based on the extending direction of the first linear part, and
• a second linear part positioned more in the tongue plate extracting direction than the inclination part and extending in parallel to the extending direction of the first linear part.