PROBLEM TO BE SOLVED: To accurately and simply evaluate delayed fracture properties of a metal material used under atmospheric corrosion environment.SOLUTION: A method for evaluating delayed fracture properties of a metal material comprises performing a step consisting of the step (A) of depositing a component mainly including chloride on a metal material and the step (B) of performing at least one cycle applying the drying step (b1) of drying the surface of the metal material by varying relative humidity and the wetting step (b2) of wetting the surface to the metal material passed through the step (A) once or more. In the step (A), the amount of the component mainly including the chloride deposited on the metal material is 1-10000 mg/m. The step (B) includes the humidity holding step (b3) of setting a temperature variation to ± 5°C or less and holding a humidity of 50-60% RH for 0.5 hour or more during a transition period when varying relative humidity between the drying step (b1) and the wetting step (b2)
