A processing system includes a sheet-shaped device, a determination unit, and a controller. The sheet-shaped device is attachable to a seat in an area from a seat surface of the seat to a surface of a backrest of the seat. The sheet-shaped device includes a sensor that detects whether a user is sitting on the seat surface and that detects whether the user is leaning against the surface of the backrest. The determination unit determines a type of sitting posture of the user by using a signal from the sensor. The controller controls a control target in accordance with the determined type of sitting posture.
