The weight sensing apparatus of this invention which is made for quick and exacting sensing of a foodstuff's weight to be cooked, includes a pair of arms extending downward from the bottom of a turntable and a pair of projections extending inward from the body of a support member which supports the rotating turntable. When the turntable rotates, the arms engage with the projections so that the support member can rotate at the same speed as that of the turntable. The plurality of guide rollers, which are rotatably connected to the support member, press down at least one or more weight sensors which are disposed in a groove offering a circular track, and thereby sensing the weight of the foodstuff quickly and exactly.