Clearance sensor

A clearance sensor comprising:

• an electrode member including a columnar detection electrode including a detection end surface on a first end side with respect to an axial direction along a central axis of the detection electrode, the electrode member further including a guard electrode and a ground electrode having central axes coaxial with the central axis of the detection electrode;
• an insulation member connecting the detection electrode and the guard electrode to each other, and connecting the guard electrode and the ground electrode to each other;
• an insulation layer filling a gap between the detection electrode, the guard electrode, the ground electrode, and the insulation member;
• and
• a cooling flow path penetrating the electrode member and the insulation member in the axial direction along the central axis of the detection electrode,
• wherein the electrode member and the insulation member are locked to each other in at least one of the axial direction along the central axis and a direction around the central axis, and
• wherein the cooling flow path opens at the detection end surface on the first end side of the detection electrode with respect to the axial direction along the central axis of the detection electrode.