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A novel and highly sensitive hot-wire-type flow sensor constructed of a YBa2Cu3O7-δ thin film has been fabricated. When heating voltage was applied to the sensor, a hot spot appeared and the sensor had a high sensitivity to air flow speeds of 0.04-4 m/s. Sensing characteristics have been examined for two different heating modes, constant-voltage and constant-resistance. In the constant-voltage mode, the current was proportional to the square root of the flow speed. In the constant-resistance mode, the output voltage was proportional to the fourth root of the flow speed, as is explained by the well-known King's law. In both cases, high sensitivity and good linearity were observed.