The nonlinear interaction of an ultrashort‐pulse laser with a solid target is investigated by using a newly developed particle simulation code, which enables the analysis of laser–plasma interaction in the very steep density gradient in which the laser light penetrates into an overdense plasma. For an ultrashort laser pulse, the plasma density scale lengthLdsatisfiesLd≤r0for an electron excursion lengthr0. Laser absorption and electron acceleration processes are proposed for the above situation. It is found that the wave breaking is the main mechanism of the electron acceleration and laser absorption, as is discussed in Brunel’s paper [Phys. Rev. Lett.59, 52 (1987)].