A seal ring dismounting device includes a handle and a first section of a shank is connected to the handle, a second section is connected to the first section at an angle. The second section includes first teeth defined in a lower side thereof. An operation plate having hook portion is connected to the second section. A rod is connected to a U-shaped frame and includes second teeth which are engaged with the first teeth of the second section. A spring member is located between the frame and the second section so that when pushing the frame toward the second section, the rod is moved to disengage the second teeth from the first teeth such that the rod can be easily moved along the second section.