To prevent a circuit board and circuit board wiring from being damaged at the time of assembling a physical quantity detection device. A physical quantity detection device of the present invention is characterized by having, on a circuit board, a sensor unit wherein a flow rate detection unit is disposed, a circuit unit wherein a circuit element is disposed, and a partitioning wall that partitions the sensor unit and the circuit unit from each other. The physical quantity detection device is also characterized in that an internal layer conductor for electrically connecting the flow rate detection unit and the circuit unit to each other is provided on a circuit board internal layer where the partitioning wall is positioned.