Abstract: A flow sensor functions as a flow meter, for measuring the flow rate of a measurement objective fluid. The flow sensor comprises a flow passage, through which the measurement objective fluid flows, a sensor arranged so as to face the flow passage from a top wall that defines the flow passage, a throttle surface opposed to the top wall where the sensor is arranged, and an inclined surface provided on an upstream side of the throttle surface. The inclined surface is disposed such that the flow passage widens toward the inlet side of the flow passage. The inclined surface has an angle such that an extension line thereof passes through a position that is offset toward the upstream side, as compared to the detecting section of the sensor.