A method for replenishing a development replenisher in an automatic developing machine for a photosensitive lithographic printing plate precursor, wherein a value of an electric conductivity of a developer obtained by measuring an electric conductivity is compared with a reference value, and a development replenisher is replenished to the developer when the value of the developer is lower than the reference value, the method comprising: using a reference value of an electric conductivity optimal for a high resolution image as the reference value when developing a precursor having an exposed high resolution image in which an output datum of 50% area ratio is 210 lpi or more in terms of a peripheral length of an image area in an image unit that constitutes a gradation of a screen image: and changing the reference value to an ordinary reference value when developing a precursor not having a high resolution image.