A positioner is provided with a control calculating portion 1 including first and second calculating portions. The first calculating portion, a valve opening detecting portion, and a first pressure sensor are contained in a first case. The second calculating portion, an electropneumatic converting portion, a pneumatic circuit portion, and a second pressure sensor are contained in a second case. The first case is assembled together with the valve, and the second case is located in a position away from the valve. Output signals from the first calculating portion, which are a control signal MV (a PWM signal) and a detected pressure signal S1′ (wherein a detected pressure signal S1 has been converted into a digital signal, are sent to the second calculating portion through cables 16.