We extend the geometric Hamilton-Jacobi formalism for Hamiltonian mechanics to higher-order field theories with regular Lagrangian density. We also investigate the dependence of the formalism on the Lagrangian density in the class of those yielding the same Euler-Lagrange equations.The Hamilton-Jacobi (HJ) formalism is a cornerstone of the calculus of variations (see for instance [1]) and the theory of Hamiltonian systems. Moreover, it is a first important step through the quantization of a mechanical system (see, for instance [2], see also [3]). HJ formalism can be readily extended to first-order Lagrangian (and Hamiltonian) field theories [1,4]. Moreover, both its original version and its first-order field theoretic extension have an effective geometric formulation in terms of symplectic [5] and multisymplectic [7-9] geometry respectively. Finally, in [6] the authors formulate in geometric terms a generalized HJ problem depending on the sole equations of motion (and not directly on the Lagrangian, nor the Hamiltonian function itself). In particular, such generalized problem can be stated for any SODE on the tangent bundle and any vector field on the cotangent bundle of a configuration manifold, and thus it has a wide range of applicability. The aim of the present paper is to formulate in geometric terms a (generalized) HJ problem for higher-order Lagrangian field theories, in view of its application to both variational calculus and theoretical physics. Recall that higher-order Lagrangian field theory has got a very elegant geometric formulation (see, for instance, [10]). Moreover, the Hamiltonian formulation of Lagrangian mechanics has been recently extended to