To constitute a seating sensor inexpensively by punching a film sensor of an approximately half size of a seat to an optional continuous linear shape and unfolding an inner part and an outer part of the punched linear shape flatly with an end side at its center.

A serpentine notch 7 is provided to a left half face of a film sensor A starting from a point P spaced by several cm from a lower end 8 of the sensor. Reaching an upper part, the serpentine notch 7 is similarly provided to a right half face to a point Q away (above) by several cm to the side end 8. The notch 7 is a continuous curve or line, or a combination of the lines. The film sensor A is separated at the notch 7 and unfolded flat centering a line connecting the points P and Q. Since the film sensor A is increased in size to approximately double, it is possible to detect a pressure applied to an entire seat face by the film sensor A of an approximately half size of the seat.