To obtain an electrode plate attaching/detaching device of a wet developing apparatus with which the wet developing apparatus can simply be disassembled and can easily be reassembled after cleaning parts at the outside of a machine.

In a wet platemaking machine in which a developing solution is jetted on a photosensitive surface of a photosensitive sheet brought onto an electrode plate by a roller in an intake section to develop an electrostatic latent image and the surplus developing solution on the master sheet is removed by a pair of squeezing rollers located at opposite side edges of the electrode plate, the electrode plate attaching/detaching device of a wet developing apparatus is configured by fitting a frame of a developing tank facing the electrode plate of the squeezing roller sides with a support shaft in the transverse direction, forming U-shaped grooves capable of engaging with the support shaft in side plates of the electrode plate, attaching a pair of manually operable latch members to both side edges in the transverse direction just beneath the electrode plate in an energized state by energizing springs, and attaching latch pins to the corresponding side edges of the electrode plate.