PURPOSE: To prevent hanging down of a buckle for connection from occurring, by a method wherein the above mentioned buckle is made nonrotatable by providing a cam body unitarily on the buckle for connection fixed to a through belt rotatably and by connecting with the cam body at the time of housing of the through belt.

CONSTITUTION: An end of a main body 21 of a through belt is fixed to a roof side rail 1 rotatably. A circular cam body 29 having a connecting protruded part 28 is hinged rotatably by the other end of the main body 21 of the through belt, and a buckle 30 for connection is formed on the said cam body in a body. In addition to the above, a retaining component 32 movable toward the cam body is energized always by a spring 35 and provided on the main body 21 of the through belt. A rod 34 of the retaining component 32 is connected with a stationary component 26 through a connecting component 37. Then, when the main body 21 is in an operating position, connection with the above-mentioned protruded part 28 is disconnected by retracting the retaining component 32. Then, the buckle 30 becomes nonrotatable as the retaining component 32 is protruded and connected with the protruded part 28 when the main body 21 is in a housing position.