PROBLEM TO BE SOLVED: To provide a sensor which can reduce a cost and be provided with the appropriate humidification and conductivity as the sensor.SOLUTION: A sheet sensor 20 is provided with a surface layer 22 that forms a surface of a seat to be in contact with a human body, a conductive layer 24 having a humidified gas diffusion layer 28 interposed that has two or more gaps using a lattice mesh material inside, an electrode layer 30 formed as an electrode part, and two or more through-holes 31 for passing humidified gas sent from humidified gas generator, thereby providing the appropriate humidification and conductivity to the sensor.
