a support spring 16 is provided at the bottom of said bleach fixing tank 12 so as to apply a supportive raising force to the bottom of tank 12 by means of said spring 16 in order to reduce the negative load on the motor when the pinion is rotated to raise the bleach fixing tank 12 in this developing unit 10 light sensitive material 1 is sequentially guided through developing tank 11 bleach fixing tank 12 and stabilizing tank 13 by means of transport rollers 6 the aforesaid pinion 15 is rotated by means of a motor in the direction which raises the bleach fixing tank 12 as shown in fig2 said bleach fixing tank 12 thereby being raised until the top edge of rack 14 provided on side wall 12b of said tank 12 reaches a first microswitch 17 disposed thereabove said tank 12 then being supported at said position on the other hand when developing unit 10 is moved to perform routine maintenance or to clear a paper jam or the like pinion 15 is rotated by means of a motor in the direction which lowers the bleach fixing tank 12 i e in the reverse direction as shown in fig3 said bleach fixing tank 12 thereby being lowered until the bottom edge of rack 14 reaches a second microswitch 18 disposed therebelow and said tank 12 then being supported at said position thus when only the bleach fixing tank 12 is.