To provide a truck roof structure for reducing the air resistance generated in a stepped part between a cab and a cargo bed, and reducing manufacturing cost.

In the truck roof structure constituted so that a cargo bed 8 higher than a roof 2 is arranged behind a cab 1, an upper stepped part 12 extending in the vehicle width direction is provided on the roof 2 of the cab 1, and the upper stepped part 12 is arranged at the position of 0.4 to 0.7 in terms of the roof length ratio in the vehicle longitudinal direction from a forward end of a flat roof surface 7. The air flowing over the roof 2 is guided upward of the cargo bed 8 so as to avoid a stepped part 9 between the cab 1 and the cargo bed 8, and the air resistance received by the stepped part 9 is reduced thereby. Further, a wind deflector fitted to eliminate the stepped part 9 between the cab 1 and the cargo bed 8 can be omitted, and a manufacturing cost can be reduced.