A thermal flow meter has improved measurement accuracy due to the shape of a circuit package. The circuit package has a measurement surface and a backside of a measurement surface of a rear surface thereof is located in a bypass passage, the bypass passage being configured to allow a measurement target gas to flow therein dividing the measurement target gas into a flow path at a side of the measurement surface and a flow path at a side of the backside of measurement surface of a rear surface thereof. An inflow-side end surface of the circuit package has different shapes at the side of the measurement surface and at the side of the backside of the measurement surface.