To provide a safety mechanism structure of a hook lock capable of supporting an operation lever in a stable condition, and releasing a safety hook with excellent operability.

A finisher cover 5 to cover a space between a radiator core support 1 and a front grille G is provided above the radiator core support 1, and an operation lever 25 connected to a safety hook 23 across a heat exchanger 3 extends forward of a vehicle while penetrating the finisher cover 5. A substantially center portion of the operation lever 25 is pivotably supported by the finisher cover 5 via a hinge part 32, and the safety hook 23 is released by functioning a tip part of the operation lever 25 as a power point, the hinge part 32 as a fulcrum and a base end part of the operation lever as a point of action.