A flow meter which comprises a body part (2) having a main channel (7) through which a fluid to be measured flows and a branch section (9) which branches the fluid from the main channel (7), and a fluid measurement part (3) having a sensor (15) which detects the fluid introduced from the branch section (9) and measuring the fluid according to the result of the detection by the sensor (15). An orifice (8) which applies differential pressure for making the branch section (9) branch the fluid is integrated with the main channel (7).
