To solve the problems of the conventional mat sensor that it is sensitive to the projecting and recessed surfaces, so that when using with a large amount of deformation and with a large bent, malfunction is liable to occur, when vibration or friction is applied, aluminum foil or evaporation film wears away in an opening to easily cause conducting failure, and it is easily damaged due to torsional movement and shifting.

The mat sensor includes: surface protective sheets for insulating and protecting a sensor; a pair of upper and lower opposite electrode sheets; and an insulating spacer sheet having a plurality of openings and compressed and deformed by load, between the electrode sheets. The mat sensor adopts a fixing method, wherein the electrode sheets are fixed to the surface protective sheets, and further the outer peripheries of the surface protective sheets are prevented from hitting against the spacer and electrode sheets. Further, a lead wire is fixed together with the surface protective sheets with the lead wire projecting outside the surface protective sheets. The spacer uses polyester fiber as base fiber.