Provided herein is a magnetostriction element having a large power output and a high power density. The magnetostriction element is comprised of a magnetostrictive material that is a monocrystalline alloy represented by the following formula (1), Fe(100-α-β)GaαXβ,  Formula (1) wherein α and β represent the Ga content (at %) and the X content (at %), respectively, X is at least one element selected from the group consisting of Sm, Eu, Gd, Tb, Dy, Cu, and C, and the formula satisfies 5≤α≤40, and 0≤β≤1.