Abstract: A clearance sensor includes: a columnar detection electrode having a detection end surface on one end side in the axial direction of the center axis; an electrode member including a guard electrode and a ground electrode having the center axis coaxial with that of the detection electrode; an insulating member linking between the detection electrode and the guard electrode, and linking between the guard electrode and the ground electrode; and an insulating layer filling the spaces between the detection electrode, the guard electrode, the ground electrode, and the insulating member, wherein the space between the electrode member and the insulating member is retained in the axial direction and/or the direction around the axis of the center axis.