A method for obtaining a maximum horizontal stress at a depth of a geological formation, includes: setting an estimate SHmax of the maximum horizontal stress; conducting an elastoplastic modeling simulation of the geological formation around a wellbore with the estimate SHmax and obtaining a simulated value ϕb,1 of a breakout angle, wherein the breakout angle is a half-width of a breakout region; and upon determining that the estimate ϕb,1 is greater than or equal to a prescribed value and is different from a measured breakout angle ϕb,m at the depth by more than a threshold value, repeatedly changing the estimate SHmax and conducting the elastoplastic modeling simulation.