Seat with seat sensor

A seat with a seat sensor allowing easy manufacture is provided. Though the seat is provided with the seat sensor for detecting an occupant seated in the seat, the occupant never feel bad touch due to the presence of the sensor. A cavity 5 is formed upward from the bottom of a pad 1 and a sensor 2 is provided inside the cavity 5. A slab 6 is filled in the cavity 5 to close the cavity. The slab 6 is made of the same soft material as that of the pad 1. The cavity 5 is formed such that the opening thereof is narrow, thereby preventing the slab 6 from coming off.