To provide the effective technique related to the peel-off prevention of the interior material attached to the inner wall of a tunnel.

A peel-off characteristic measuring instrument for measuring the peel-off characteristics of the interior material attached to a tunnel substrate by an attachment implement is equipped with a cover body for covering the interior material attached to the tunnel substrate using an attachment implement, an exhaust means for exhausting air in the space covered with the cover body; an air supply means for supplying air into the space covered with the cover body; a displacement meter for measuring the displacement quantity of the attachment implement; and a displacement meter for measuring the displacement quantity of the interior material.