A seat-weight sensor includes a load cell having a load sensor arranged therein and a support for holding a support shaft of the load cell. The support includes a convex portion to hold the support shaft and a pair of flange portions arranged at both sides of the convex portion and fixed to a vehicle floor side. The support has a pair of slots arranged at a perimeter of the convex portion and for reducing a physical effect that the pair of flanges provides to the convex portion.