The present embodiments provide an acceleration sensor, which enables highly accurate detection and has an extremely compact size. The acceleration sensor of the present embodiments is provided with a substrate, a anchor portion formed on the substrate, a support beam, which has one end connected to the anchor portion and extends across a space from the substrate, and a proof mass which is connected to the other end of the support beam and held across a space from the substrate. The acceleration sensor is further provided with first and second piezoelectric bending resonators, a comparison unit, and a calculation unit. The first and second piezoelectric bending resonators have one end connected to the anchor portion and the other end connected to the proof mass or the support beam and have a stack of a first electrode, a first piezoelectric film, and a second electrode. The first and second piezoelectric bending resonators extend on the both sides of the support beam and perform bending resonance motion in a direction perpendicular to the piezoelectric film. The comparison unit measures a difference of a resonance frequency between the first and second piezoelectric bending resonators. The calculation unit calculates an acceleration in a direction perpendicular to the extending direction of the support beam in the substrate surface from the difference of the resonance frequency.