An acoustic transducer has a substrate having a cavity that is open at a top of the substrate, a vibration electrode film provided above the substrate so as to cover the cavity, and a fixed electrode film provided a distance above the vibration electrode film. A gap is formed between an upper surface of the substrate and a lower surface of the vibration electrode film around the cavity. In the gap across which the upper surface of the substrate and the lower surface of the vibration electrode film face each other, a narrow portion of the gap that is narrower than another portion of the gap is disposed. The narrow portion of the gap extends linearly.