The present invention is to, in an automatic flat belt fixing device for trucks, resilient second direction check unit 50, between spaced apart from each other the first side wall plate 11 of the truck automatic flat belt fixing apparatus is formed of the side wall plate the lower connection portion 15 formed on the 11 flat belt (B) or the combined blood and that connection of the vehicle fixture (10); Second side wall panel 21, a lifting-type locking part (60) between the formed the fixture 10, the total 20 times that are rotatably connected to the intermediate an upper and a shaft member 30 that are spaced apart from each other and .; The top and above the fixed body 10, the rotating body 20 and each rotatably connected to a lower portion of the flat belt (B) a shaft member (30) for a flat belt janghom 31 is formed long in the longitudinal direction to be inserted Wow; The shaft ratchet gear (40) or a side of the member 30 having the directional teeth are formed on both sides and; And the first side wall plate 11 is provided between the resilient second direction check having a check piece 51, to prevent the other rotating in the direction in which the one-way rotation of the ratchet gear 40, but can be of the fixture (10) parts ( 50); Once the second side wall panel 21 lifting possibly formed descent when clamping members (61) between the body (20) is stuck in the ratchet gear 40 teeth rotates the rotor 20 in one direction, and the rotating body on the truck automatic flat belt fixing apparatus characterized in that comprises a; 20, the shaft member 30 and the ratchet gear 40, the lifting type locking part (60) for rotatably in one direction integrally will be.