To execute development after a latent image formed on exposed photosensitive material is sufficiently stabilized without complicating the constitution of the device by providing an auxiliary tank having a casing in which a heat insulating means and a carrying means are housed on the upstream side of a developing tank.

The auxiliary tank 134, the developing tank 136, a fixing tank 138, washing tanks 140a, 140b, 140c and 140d are successively provided in a photosensitive material processing device 130. After the latent image is stabilized by sensitizing the latent image in the tank 134, the photosensitive material which is color-developed, bleach-fixed and washed by processing solution with which each tank is filled is fed to a drying part 142 and ejected to a sorter 144. In the tank 134, a specified time required to sensitize and stabilize the latent image from exposure till charging developer is secured for the exposed photosensitive material, and the temperature of the photosensitive material is held to temperature suitable for the prevention of sensitizing the latent image, the stabilization of the latent image and developing processing in a next stage.