Flow meter including increased measuring detection accuracy

A flow meter comprising:

• a cylindrical measurement tube including an inlet through which liquid enters and an outlet through which the liquid flowing from the inlet exits, and having an internal flow passage extending along an axis;
• and
• a temperature detecting substrate having a heating resistance element and a temperature detecting resistance element formed on a detection surface thereof along the axis, wherein
• an outer circumferential surface of the measurement tube is provided with a flat surface arranged as opposed to the detection surface of the temperature detecting substrate, and a pair of recesses arranged so as to sandwich the internal flow passage at a position where the heating resistance element is arranged on the axis,
• the flat surface and the detection surface are bonded together to form a planar bonding area having a width in a direction orthogonal to the axis,
• the planar bonding area includes a first bonding area corresponding to a first portion on the axis where the pair of recesses is arranged and a second bonding area corresponding to a second portion on the axis where the pair of recesses is not arranged, and
• the width of the first bonding area in a direction orthogonal to the axis is narrower than the width of the second bonding area in a direction orthogonal to the axis.