To prevent erroneous measuring without having to set a measuring precision higher than required while maintaining a sufficient measuring precision and prevent a steep rise in operation costs.

This seating weight measuring apparatus is provided with a supportor 14 having one end of which the relative position is fixed to a vehicle body and the other end which displaces itself according to the amount of load from the side of a seat of a vehicle; a permanent magnet 19 which is provided for the one end of the supportor 14 and which opens at least to both ends of the vehicle body in horizontal directions; a holder 18 having a middle part held at the other end of the supportor 14 and having a shape retaining property, and a detector 20 provided for a tip of the holder 18 and opposed to the permanent magnet 19 in an isolated state.