An anodized layer formation method includes: providing an aluminum film provided on a support or an aluminum base; and forming a porous alumina layer which has minute recessed portions by applying a voltage between an anode which is electrically coupled to a surface of the aluminum film or the aluminum base and a cathode which is provided in an electrolytic solution with the surface of the aluminum film or the aluminum base being in contact with the electrolytic solution. The forming of the porous alumina layer includes increasing the voltage to a target value and, before the voltage is increased to the target value, increasing the voltage to a first peak value which is lower than the target value and thereafter decreasing the voltage to a value which is lower than the first peak value. As such, an anodized layer with reduced variation of recessed portions can be formed.