a peeling detector for a tunnel wall capable of rapidly inspecting the tunnel wall by effectively using infrared radiation is provided . the detector heats a tunnel wall 1 with a light emitting heater 4 while moving . an infrared camera 6 detects infrared radiation radiated by the wall after heating . based on the quantity of the infrared energy , a difference in the temperature between peeled and normal portions induced by heating is grasped to evaluate whether the peeling of the tunnel wall 1 is present or not .