Thermal flow meter

A thermal flow meter comprising:

• a measurement tube having an inflow port and an outflow port, having an internal flow channel formed extending along an axis, having a flat surface formed to a part of an outer circumferential face of the measurement tube, and formed of a resin material, wherein a liquid flows into the inflow port, and the liquid flowing in from the inflow port is allowed to flow out of the outflow port;
• a temperature detecting substrate having a heating resistance element and a temperature detecting resistance element formed on a flat detection surface along the axis, the detection surface being joined to the flat surface of the measurement tube along the axis;
• and
• a sheet arranged between the flat surface of the measurement tube and the detection surface of the temperature detecting substrate so as to cover the flat surface and configured to prevent a gas volatilizing from the liquid and permeating the measurement tube from reaching the detection surface,
• wherein a first face of the sheet is joined to the flat surface of the measurement tube, and
• wherein a second face of the sheet is joined to the detection surface of the temperature detecting substrate.