A physical quantity sensor includes: a movable body; a support that supports the movable body via a coupler; a substrate that is disposed so as to overlap the movable body in a plan view and is provided with a first fixed electrode and a second fixed electrode thereon along a first direction orthogonal to a longitudinal direction of the coupler; a third fixed electrode that does not overlap the movable body in the plan view, is electrically connected with any one of the first fixed electrode and the second fixed electrode, and is provided on the substrate; and a first dummy electrode that is disposed next to the third fixed electrode in the plan view, is at the same potential as the movable body, and is provided on the substrate.