A fluid controller that allows facilitated installment, piping and wiring connection to semiconductor manufacturing equipment and does not corrode even when a corrosive fluid is used, includes a flowmeter sensor section having a first ultrasonic transducer which transmits ultrasonic waves in a fluid and a second ultrasonic transducer which receives the ultrasonic waves transmitted from the first ultrasonic transducer and outputs the signal thereof to a flowmeter amp section. An adjustment valve that adjusts the flow rate of the fluid using operation pressure is provided, and at least the flowmeter sensor section and the adjustment valve are connected to and disposed in a casing having a fluid inlet and a fluid outlet.