Provided is a thermal flow meter including an inlet-side body into which an inlet of a measurement tube is inserted, an outlet-side body into which an outlet of the measurement tube is inserted, an inlet-side nut having internal threads fastened to external threads formed on the inlet-side body, an outlet-side nut having internal threads fastened to external threads formed on the outlet-side body, an inlet-side ferrule of resin being deformed to form a seal area as the inlet-side nut 15a is fastened to the inlet-side body, and an outlet-side ferrule of resin being deformed to form a seal area as the outlet-side nut is fastened to the outlet-side body.