A physical quantity sensor includes a movable flat plate having a plurality of openings passing therethrough that is swingable around an axis of rotation, a support substrate linked to the flat plate via a column to suspend the movable flat plate over the support substrate via a gap, and a protrusion protruding toward the movable element. In a plan view, the openings are excluded from a D/2-width annular range surrounding the outer circumference of the protrusion, where D is the maximum outer diametrical dimension of the protrusion.