In an acceleration sensor, a sensor unit includes a weight portion having a recess section with one open surface and a solid section one-piece formed with the recess section, beam portions for rotatably supporting the weight portion such that the recess section and the solid section are arranged along a rotation direction, a movable electrode, fixed electrodes, detection electrodes electrically connected to the fixed electrodes to detect a capacitance between the movable electrode and the fixed electrodes. A fixed plate is arranged in a spaced-apart relationship with a surface of the weight portion on which the movable electrode is provided, and embedment electrodes are embedded in the fixed plate to extend along a thickness direction of the fixed plate, the embedment electrodes having one end portions facing the movable electrode to serve as the fixed electrodes and the other end portions configured to serve as the detection electrodes.