Provided is an acoustic sensor. The acoustic sensor includes: a substrate including sidewall portions and a bottom portion extending from a bottom of the sidewall portions; a lower electrode fixed at the substrate and including a concave portion and a convex portion, the concave portion including a first hole on a middle region of the bottom, the convex portion including a second hole on an edge region of the bottom; diaphragms facing the concave portion of the lower electrode, with a vibration space therebetween; diaphragm supporters provided on the lower electrode at a side of the diaphragm and having a top surface having the same height as the diaphragm; and an acoustic chamber provided in a space between the bottom portion and the sidewall portions below the lower electrode.