A structure of a coreless crawler comprising: main cords that are embedded in rows in a longitudinal direction of the crawler, two layers of bias cords (a, b) that are embedded at an outer peripheral side of the main cords, bias cords (c) that are laid perpendicular to the main cords and embedded at an inner peripheral side of the main cords, rubber protrusions that are formed at constant intervals at a central portion on an inner peripheral surface of the crawler, and rubber lugs that are formed on an outer peripheral surface of the crawler, wherein the bias cords (a, b, c) and the main cords are held between treatment rubbers, and a rubber layer having lower hardness than treatment rubber is interposed between the main cords and the bias cords (c).