To provide a seal mechanism of the passage part of passing-through things in the partition portion of a vehicle, with a reasonable structure which can be installed easily and can satisfy seal functions.

This is a seal structure which can perform seal functions in the passage part of string-type soft things or stick-type things like a hose and wiring harness or the like passing through a partition portion 50 in a vehicle. It comprises a partition board 3 made of an elastic material and provided with passage-retaining holes 6, 6' almost equal to the outer diameters of passing- through things 30, 31 and corresponding to the number of the passing through things, and cut lines 7 running from the edges of the holes to outer circumference, and a grommet 2 made of an elastic material, which has an opening 2a fitted and engaged with the partition board 3 and which can be engaged and fixed with a side-partition hole 51 of the vehicle.