To provide a weight sensor which can detect objects such as from a light weight (in gram unit) to a heavy weight (in ton unit), which has excellent durability by using structural material without sensitivity deterioration, and which can be installed and used at low cost as a detection sensor most suitable for an outdoor detection area having a wide range (in area and in distance).

A weight sensor comprises: insulation spacers 4 having elasticity and a band, rectangular or circular shape; an electrode E-3b and an electrode S-3a made by an aluminum resin composite panel, both constituting an electrode by attaching the insulation spacers 4 therebetween; insulation bodies 2 disposed via the electrode E-3b and the electrode S-3a; reinforcing aluminum plates 1 disposed via the insolation bodies 2 to form an integrated plate as a whole; shields 6 being flexible such as an aluminum foil laminate film, and covering outer periphery portions between the reinforcing aluminum plates 1; waterproof tapes 7 covering the shields 6 to shield them; and a cover insulation body 5 being flexible depending on weight applied thereon, having a sealed structure, and covering around the reinforcing aluminum plates 1 to form a double sealed structure.