An electronic throttle control unit for an engine can perform precise control by using a single inexpensive AD converter. The unit includes an electronic throttle that controls an engine, a throttle opening detection section that detects the throttle opening of the electronic throttle, and a control section that controls the throttle opening to a target value in accordance with an operating condition of the engine. The throttle opening detection section includes a throttle opening sensor that generates a sensor voltage corresponding to the throttle opening, an offset part that converts the sensor voltage into a plurality of voltages with offsets, a distribution circuit for distributing the voltages with offsets to a single path, an AD converter that AD converts the voltages distributed to the single path; and a distribution switching section that performs distribution switching control of the distribution part, wherein the distributed voltages are detected as a final throttle opening to be controlled.