A passenger's weight measurement device 1 comprises a left and right pair of fixed lower rails 3 which are fixed on the vehicle floor, a left and right pair of movable upper rails 4 which are disposed to move in a front-and-rear direction on the fixed lower rail 3, load sensors 50 and 60 which are fixed to an upper surface of the right movable upper rail 4, load sensors 70 and 80 which are disposed on the movable upper rail 4 to be movable in a left-and-right direction with respect to the right movable upper rail 4, a sub frame 110 which is mounted on the load sensors 50, 60, 70, and 80, side frames 141 and 142 which are welded to the sub frame 110, and a pan frame 143 which is detachably disposed to the side frames 141 and 142 to cover the front of the side frames 141 and 142. A gouged section 151 is formed on the side frame 141, A rear connecting member 113 ties the two rail members together near the rear sensors, and another connecting member 5, which has a width that is wider at either end than it is in the center, ties the two rail members together forward for the rear load sensors.