Ising machines are currently under active investigation as dedicated computers for combinatorial optimiza- tion problems. A hardware limitation of Ising machines is that the energy function must be prepared as a quadratic expression in binary variables, and order reduction must be performed if the problem contains terms of third or higher order in the binary variables. The purpose of this study is to clarify the solution performance of the Ising machine for problems in which the objective function contains terms of higher than the third order of the binary variable in a naive formulation. To this end, the solution performance of the Ising machine was investigated on the subject of artificially generated vehicle routing problems considering leveling.